compare element in two arrays - javascript

I want to compare each element of array real with each element of array number. And if there is any matches push them in array add so I can see them. In this case add must be 2,3,6,10,14 if code is good.
<!DOCTYPE html>
<html>
<head>
</head>
<body>
<script>
var real=[1,2,3,4,5,6,7,8,10,14,16,233,235,245,2,5,7,236,237];
var number=[2,3,6,10,12,13,14,172,122,234];
var add=[];
for (k=0; k<number.length; k++)
{
for (w=0; w<real.length; w++)
{
if (number[k]==real[w]);
{
add.push(number[k],real[w]);
}
};
};
document.write(add+"<br>");
</script>

Here is a short and simple solution using Array.forEach and Array.indexOf functions:
var real = [1,2,3,4,5,6,7,8,10,14,16,233,235,245,2,5,7,236,237],
number = [2,3,6,10,12,13,14,172,122,234],
add = [];
real.forEach(function(v) {
if (number.indexOf(v) !== -1 && this.indexOf(v) === -1) this.push(v);
}, add);
console.log(add); // [2, 3, 6, 10, 14]

A more elegant and readable solution:
var matched = [];
real.forEach(function(realNum) {
number.forEach(function(numberNum) {
if(realNum == numberNum && matched.indexOf(realNum) === -1) {
matched.push(realNum);
}
});
});

Here's one way you can do it using ES6:
var real = [1, 2, 3, 4, 5, 6, 7, 8, 10, 14, 16, 233, 235, 245, 2, 5, 7, 236, 237];
var number = [2, 3, 6, 10, 12, 13, 14, 172, 122, 234];
var filtered = real.filter(x => number.indexOf(x) > -1);
var unique = new Set(filtered);
document.body.innerHTML = [...unique];

try this way...
Sorted the main Array, removed duplicates and the find the common elements from both the arrays.
var main = [1,2,3,4,5,6,7,8,10,14,16,233,235,245,2,5,7,236,237];
var compare = [2,3,6,10,12,13,14,172,122,234];
function compareNumbers(a, b) {
return a - b;
}
console.log('Sorted Array :', main.sort(compareNumbers) );
// Sorted Array : [1, 2, 2, 3, 4, 5, 5, 6, 7, 7, 8, 10, 14, 16, 233, 235, 236, 237, 245]
Array.prototype.unique = function() {
var unique = [];
for (var i = 0; i < this.length; i++) {
var current = this[i];
if (unique.indexOf(current) < 0) unique.push(current);
}
return unique;
}
console.log('Unique Array Elements:', main.unique() );
// Unique Array Elements: [1, 2, 3, 4, 5, 6, 7, 8, 10, 14, 16, 233, 235, 236, 237, 245]
function commonElements(arr1, arr2) {
var common = [];
for (var i = 0; i < arr1.length; i++) {
for (var j = 0; j < arr2.length; j++) {
if (arr1[i] == arr2[j] ) {
common.push( arr1[i] );
j == arr2.length; // To break the loop;
}
}
}
return common;
}
console.log('Common Elements from Both Arrays : ', commonElements(main.unique(), compare.unique()) );
//Common Elements from Both Arrays : [2, 3, 6, 10, 14]

Related

Union between three arrays

I need to find the union of three arrays that get passed to the function union.
It took me about 50lines to code to get the expected result. Apparently, the following code works but now I wonder what are the best ways (either in a functional and in a non-functional fashion) to do the same job.
function union(...arrays) {
var array1 = arguments[0];
var array2 = arguments[1];
var array3 = arguments[2];
var unique = [];
var intersaction = [];
// find the unique values
for(let i = 0; i < array1.length; i++) {
if( (array2.includes(array1[i]) == false) && (array3.includes(array1[i])) == false ) {
unique.push(array1[i]);
}
}
for(let i = 0; i < array2.length; i++) {
if( (array1.includes(array2[i]) == false) && (array3.includes(array2[i])) == false ) {
unique.push(array2[i]);
}
}
for(let i = 0; i < array3.length; i++) {
if( (array1.includes(array3[i]) == false) && (array2.includes(array3[i])) == false ) {
unique.push(array3[i]);
}
}
// find the intersection
for(let j = 0; j < array1.length; j++) {
if(array2.includes(array1[j]) || array3.includes(array1[j]) ) {
if (intersaction.indexOf(array1[j]) == -1) {
intersaction.push(array1[j]);
}
}
}
for(let j = 0; j < array2.length; j++) {
if(array1.includes(array2[j]) || array3.includes(array2[j]) ) {
if (intersaction.indexOf(array2[j]) == -1) {
intersaction.push(array2[j]);
}
}
}
for(let j = 0; j < array3.length; j++) {
if(array1.includes(array3[j]) || array2.includes(array3[j]) ) {
if (intersaction.indexOf(array3[j]) == -1) {
intersaction.push(array3[j]);
}
}
}
return union = [...intersaction, ...unique];
}
console.log(union([5, 10, 15], [15, 88, 1, 5, 7], [100, 15, 10, 1, 5]));
// should log: [5, 10, 15, 88, 1, 7, 100]
Just another solution keeping the original function signature provided by the OP:
function union(...arrays) {
return Array.from(new Set([...arrays].flat()));
}
console.log(union([5, 10, 15], [15, 88, 1, 5, 7], [100, 15, 10, 1, 5]));
Or, even shorter (but less read friendly):
return [...(new Set([...arrays].flat()))];
Explanation:
Array.from takes an Iterable as an argument, this will create a new array from the original one.
[...arrays] spreads the arrays (argument) into a new, single, one (So it becomes an array of arrays) -> [5, 10, 15], [15, 88, 1, 5, 7], [100, 15, 10, 1, 5] becomes: [[5, 10, 15], [15, 88, 1, 5, 7], [100, 15, 10, 1, 5]]
.flat flattens the array, making that an array of values rather than ar array of arrays of values -> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat -> [[5, 10, 15], [15, 88, 1, 5, 7], [100, 15, 10, 1, 5]] becomes [5, 10, 15, 15, 88, 1, 5, 7, 100, 15, 10, 1, 5]
new Set removes duplicates from the array and returns an Iterable https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set. -> [5, 10, 15, 15, 88, 1, 5, 7, 100, 15, 10, 1, 5] becomes a Set instance (an Iterable) without the duplicates. Array.from then converts the Set (Iterable) to a regular array. Further infos here: How to convert Set to Array?
BEWARE: Array.flat is currently an experimental feature (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat). Solution without using flat below:
function union(...arrays) {
return Array.from(new Set([].concat.apply([],[...arrays])));
}
console.log(union([5, 10, 15], [15, 88, 1, 5, 7], [100, 15, 10, 1, 5]));
Explanation (only differences from above):
Instead of .flat, we apply to Array.concat our original array, so that it will flatten it passing a new array as its this and providing our array as the argument: [].concat.apply([],[...arrays])
Snippet: http://jsfiddle.net/briosheje/y03osape/2/
Snippet without .flat: http://jsfiddle.net/briosheje/y03osape/4/
use set that's very simple,
The Set object lets you store unique values of any type, whether
primitive values or object
var a= [5, 10, 15];
var b=[15, 88, 1, 5, 7];
var c=[100, 15, 10, 1, 5];
var result= [...new Set([...a, ...b,...c])];
console.log(result);
I tried to copy your approach of looping over arrays but in a slightly more efficient manner, using only ES5 safe functions. I'm sure the other answers are more efficient if you can use the features they do.
var a = [1, 2, 3];
var b = [1, 2, 4, 5];
var c = [2, 7, 9];
// takes an array of arrays
function getUnique(input) {
var unique = [];
// loop over each array
input.forEach(function(item) {
// loop over each value
item.forEach(function(value) {
// if it's not already in the unique array,
if (unique.indexOf(value) == -1) {
// add it
unique.push(value);
}
});
});
return unique;
}
// takes an array of arrays
function getIntersection(input) {
// assume all elements in first array are common
var intersection = input.shift();
var remove = [];
// loop over items in first array and attempt to
// disprove commonality
intersection.forEach(function(value) {
// loop over subsequent arrays
for (var i = 0; i < input.length; i++) {
var item = input[i];
// if these arrays don't contain the value,
// then it isn't an intersection
if (item.indexOf(value) == -1) {
// add it to an array to be removed
remove.push(value);
// exit this loop
break;
}
}
});
// remove values determined not to be intersections
remove.forEach(function(value) {
intersection.splice(intersection.indexOf(value), 1);
})
return intersection;
}
var test = getUnique([a, b, c]);
console.log(test);
var test2 = getIntersection([a, b, c]);
console.log(test2);
Based on custom forEach and Reduce from previously in the exercise at http://csbin.io/callbacks
function forEach(array, callback) {
for(i = 0; i < array.length; i++){
callback(array[i])
}
}
function reduce(array, callback, initialValue) {
for(let i of array){
initialValue = callback(initialValue, i)
}
return initialValue
}
function union(...arrays) {
return reduce(arrays, (seen, next) => {
forEach(next, (element) => {
if(!seen.includes(element)) seen.push(element);
})
return seen
}, [])
}
Note if you use the in-built reduce function you can remove the empty inital array requirement.

Counting iterations of 1 in an array

My goal is to count iterations of 1 in an array.
I have this code:
var array = [10, 3, 22, 40, 1, 40, 1, 22, 1, 0, 3, 53, 1, 1];
var count = 0;
for(var i = 0; i < array.length; ++i){
if(array[i] === 1)
count++;
}
console.log(count);
Right now, it logs 5, but including "10" it should log 6, since "10" also contains a 1. What code can I use for this?
What about:
var count = array.toString().split('1').length - 1;
You can use filter method in combination with length property in order to write a more cleaner solution.
Also, use join and split methods in order to achieve your requirement.
var array = [10, 3, 22, 40, 1, 40, 1, 22, 1, 0, 3, 53, 1, 1];
console.log(array.join('').split('').filter(a=>a==1).length);
or using reduce method.
var array = [10, 3, 22, 40, 1, 40, 1, 22, 1, 0, 3, 53, 1, 1];
console.log(array.join('').split('').reduce((c,i)=> i==1 ? c+1 :c).length);
Just convert every item to string, and then check if 1 belongs to that number or not.
So for number 10, the string is '10' and then '10'.indexOf('1') equals to 0. So every time 1 is found within the string, you increment the counter.
var array = [10, 3, 22, 40, 1, 40, 1, 22, 1, 0, 3, 53, 1, 1];
var count = 0;
for (var i = 0; i < array.length; ++i) {
if (array[i].toString().indexOf('1') >= 0)
count++;
}
console.log(count);
You need to split your numbers into digits and iterate over each digit (which is a character) and compare with it. Use Object#toString to parse the number into the string, split into characters by String#split and using Array#forEach iterate over characters and do the same comparison there.
var array = [10, 3, 22, 40, 1, 40, 1, 22, 1, 0, 3, 53, 1, 1];
var count = 0;
for(var i = 0; i < array.length; ++i) {
var numberAsString = array[i].toString();
numberAsString.split('').forEach(char => {
if(char === '1') {
count++
}
});
}
console.log(count);
You'll need to convert each number to a string and use indexOf
var array = [10, 3, 22, 40, 1, 40, 1, 22, 1, 0, 3, 53, 1, 1];
var count = array.reduce(function(p,c){
if(c.toString().indexOf("1")>-1)
p++;
return p;
},0);
console.log(count);
You can Array#join the array items to a string and count using String#match with a regular expression:
var array = [10, 3, 22, 40, 1, 40, 1, 22, 1, 0, 3, 53, 1, 1];
// the || [] is a fallback in case there is no 1, and match returns null
var result = (array.join('').match(/1/g) || []).length;
console.log(result);
You could check every character of the joined string.
var array = [10, 3, 22, 40, 1, 40, 1, 22, 1, 0, 3, 53, 1, 1],
count = 0,
i,
temp = array.join('');
for (i = 0; i < temp.length; ++i) {
if (temp[i] === '1') {
count++;
}
}
console.log(count);
var array = [10, 3, 22, 40, 1, 40, 1, 22, 1, 0, 3, 53, 1, 1];
var count = 0;
for(var i = 0; i < array.length; ++i){
if( array[i] === 1 || array[i].toString().includes("1") )
count++;
}
console.log( count );

Compare two arrays simultaneously and log only the even numbers

I'm trying to compare two arrays at the same time and log the only the even values. This is the code I came up with, which does log correctly, but I'm certain this is not the correct way. How can I improve this code?
"Take arr1 and arr2 and log only the even ones"
const arr1 = [5,8,2,1,5,7,3,4,5,8,1,2,4,8,3,1,4,5];
const arr2 = [15,26,74,12,3,6,9,1,2,5];
for (var i=0; i < arr1.length; i++) {
if ((arr1[i] % 2) === 0) {
console.log(arr1[i]);
}
}
for (var i=0; i < arr2.length; i++) {
if ((arr2[i] % 2) ===0) {
console.log (arr2[i]);
}
}
Concat your arrays and then run the code on the single array.
const arr1 = [5, 8, 2, 1, 5, 7, 3, 4, 5, 8, 1, 2, 4, 8, 3, 1, 4, 5];
const arr2 = [15, 26, 74, 12, 3, 6, 9, 1, 2, 5];
const mergedArray = arr1.concat(arr2);
for (var i = 0; i < mergedArray.length; i++) {
if ((mergedArray[i] % 2) === 0) {
console.log(mergedArray[i]);
}
}
You could also just traverse both arrays in one loop and check for even numbers in both if you can't add more space. It would be even more efficient to run two for loops, where the first goes from 0 to min(arr1.length, arr2.length) and the second goes from min(arr1.length, arr2.length) to max(arr2.length,arr1.length) (of course you'd have to check to see which is bigger in advanced). Also I believe you should go here for questions related to improving the efficiency of code that runs correctly.
const arr1 = [5, 8, 2, 1, 5, 7, 3, 4, 5, 8, 1, 2, 4, 8, 3, 1, 4, 5];
const arr2 = [15, 26, 74, 12, 3, 6, 9, 1, 2, 5];
const mx = Math.max(arr1.length, arr2.length);
for (var i = 0; i < mx; i++) {
if ( i < arr1.length && (arr1[i] % 2 === 0)) {
console.log(arr1[i]);
}
if ( i < arr2.length && (arr2[i] % 2 === 0)) {
console.log(arr2[i]);
}
}

Looping through two (different lengthed) arrays to produce an alternating output

What is an efficient way of looping through two arrays to produce an alternating output? In JavaScript.
If I have two arrays like this:
var oddNumbers = [1, 3, 5, 7, 9]
var evenNumbers = [2, 4, 6, 8, 10, 12, 14]
NB: The arrays may not be the same length
How can I get the following output?
Output: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14
I would have thought this would work:
if (oddNumber.length > evenNumbers.length) {
var large = oddNumbers;
} else {
var large = evenNumbers;
}
for(var i = 0; i < large.length; i++){
if (evenNumbers.length >= i && oddNumbers.length >= i) {
console.log(oddNumbers[i] + ", " + evenNumbers[0]);
} elseif (evenNumbers.length >= i) {
console.log(evenNumbers[0]);
} else {
console.log(oddNumbers[0]);
}
}
But it's pretty messy, any better way of approaching this?
NOTE: These may not necessarily be in a numerical order, or in fact numbers
I would rather do it as follows if you just want to output them:
var oddNumbers = [1, 3, 5, 7, 9];
var evenNumbers = [2, 4, 6, 8, 10, 12, 14];
for (var i=0, j=0; i < oddNumbers.length || j < evenNumbers.length;) {
if (i < oddNumbers.length) {
console.log(oddNumbers[i++]);
}
if (j < evenNumbers.length) {
console.log(evenNumbers[j++]);
}
}
If you want to get the merge result as another array you can replace console.log with result.push to push result values on an array named result as follows:
var oddNumbers = [1, 3, 5, 7, 9];
var evenNumbers = [2, 4, 6, 8, 10, 12, 14];
var result = [];
for (var i=0, j=0; i < oddNumbers.length || j < evenNumbers.length;) {
if (i < oddNumbers.length) {
result.push(oddNumbers[i++]);
}
if (j < evenNumbers.length) {
result.push(evenNumbers[j++]);
}
}
console.log(result);
This way you iterate both arrays as long as one of them has an element that we haven't visited yet and also prevents iterating over the same index of same array twice. Please note that I used increment in if blocks to save 2 lines of code. You can also move them to the for loop since they won't break if statements.
var oddNumbers = [1, 3, 5, 7, 9];
var evenNumbers = [2, 4, 6, 8, 10, 12, 14];
var oLength = oddNumbers.length;
var eLength = evenNumbers.length;
var n = oLength > eLength ? oLength : eLength;
var rez=[];
for(i=0;i<n;i++){
if (i< oLength) rez.push(oddNumbers[i])
if (i<eLength) rez.push(evenNumbers[i])
}
console.log(rez);
var odd = ["A", "C","E","G"];
var even = ["B","D","F"];
var rez=[];
for(i=0;i<(odd.length > even.length ? odd.length : even.length);i++){
if (i< odd.length) rez.push(odd[i])
if (i<even.length) rez.push(even[i])
}
console.log(rez);
The following function accepts two arrays and returns their interleaved values as a new array:
function interleaveArrays(a, b) {
var array = [],
limit = a.length >= b.length ? a.length : b.length;
index = 0;
while (index < limit) {
a[index] && array.push(a[index]);
b[index] && array.push(b[index]);
index += 1;
}
return array;
}
Calling the function like so:
var oddNumbers = [1, 3, 5, 7, 9],
evenNumbers = [2, 4, 6, 8, 10, 12, 14];
console.log(interleaveArrays(oddNumbers, evenNumbers));
Yields:
[ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14 ]
You can then output this in your preferred manner; e.g:
var interleaved = interleaveArrays(oddNumbers, evenNumbers);
// as a loop
interleaved.forEach(function (n) {
console.log(n);
})
// or as a string
console.log(interleaved.join(', '));
// etc.
Hope this helps :)
I'd do something like this.
large = (oddNumber.length >= evenNumbers.length) ? oddNumbers : evenNumbers;
small = (oddNumber.length < evenNumbers.length) ? oddNumbers : evenNumbers;
for(var i = 0; i < large.length; i++){
if(small.length <= i + 1){
console.log(small[i] + ", "+ large[i]);
}
else {
console.log(large[i]);
}
}
A long-hand example of how it can be done. The code can be shrunk for a final solution. The basic principle I'm using is to even out the lengths to take care of the alternating then tag on the tail
var oddNumbers = [1, 3, 5, 7, 9];
var evenNumbers = [2, 4, 6, 8, 10, 12, 14];
var oLength = oddNumbers.length;
var eLength = evenNumbers.length;
var oTemp, eTemp, remainder;
if(oLength > eLength) {
eTemp = evenNumbers;
oTemp = oddNumbers.slice(0, eLength);
remainder = oddNumbers.slice(eLength);
} else if (eLength > oLength) {
eTemp = evenNumbers.slice(0, oLength);
oTemp = oddNumbers;
remainder = evenNumbers.slice(oLength);
} else {
eTemp = evenNumbers;
oTemp = oddNumbers;
remainder = [];
}
var final = [];
for(var i=0; i < eTemp.length; i++) {
final.push(oTemp[i]);
final.push(eTemp[i]);
}
final = final.concat(remainder);
alert(final);
I would simply merge the two array and sort it
var oddNumbers = [1, 3, 5, 7, 9];
var evenNumbers = [2, 4, 6, 8, 10, 12, 14];
var mergedArr=oddNumbers.concat(evenNumbers );
console.log(mergedArr.sort(function(a,b){return a-b;}));
See No loop.. No hassle. Very Simple
There will be an extra , on the screen. Add an if statement if you don't want that
for(var i = 0; i < large.length; i++){
if(i<evenNumbers.length)
console.log(evenNumbers[i]+",");
if(i<oddNumber.length)
console.log(evenNumbers[i]+",");
}
try this it will work always either number Array or String Array:
var oddNumber = [1, 3, 5, 7, 9]
var evenNumber = [2, 4, 6, 8, 10, 12, 14]
var margedNumbers = oddNumber.concat(evenNumber);
console.log("before: "+margedNumbers);
margedNumbers.sort(function(a, b){return a-b})
console.log("after: "+margedNumbers)
My solution
var oddNumbers = [1, 3, 5, 7, 9]
var evenNumbers = [2, 4, 6, 8, 10, 12, 14]
var extraElements = (oddNumbers.length > evenNumbers.length) ? oddNumbers.slice(evenNumbers.length) : evenNumbers.slice(oddNumbers.length);
var finalArr = [];
var small = (oddNumbers.length < evenNumbers.length) ? oddNumbers : evenNumbers;
small.forEach((each, index) => {
// merge elements in desired order
finalArr.push(oddNumbers[index]);
finalArr.push(evenNumbers[index]);
})
finalArr = finalArr.concat(extraElements);
alert(finalArr);
Extract the extra elements which makes both array of same length. Then, in a simple iteration, push elements from both array with same index.

Spiral traversal of a matrix - recursive solution in JavaScript

I'm trying to come up with a solution that takes in a matrix like this:
[[1,2,3,4],
[5,6,7,8],
[9,10,11,12],
[13,14,15,16]]
and returns an array traversing the array as a spiral, so in this example:
[1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10]
I'm having trouble getting this recursive solution to work, in which the result array takes the first array, the final elements of the rest of the arrays, the bottom array in reverse order, and then the first elements of the middle arrays, and then reforms the array without that outer "shell" so that it can be recursively called on what's left until there's an array of one element in the center or a 2x2 matrix (my base cases, although the latter might not be necessary...)
My solution, which doesn't work, is as follows. Any suggestions on how I can make this work?
var spiralTraversal = function(matriks){
var result = [];
var goAround = function(matrix) {
var len = matrix[0].length;
if (len === 1) {
result.concat(matrix[0]);
return result;
}
if (len === 2) {
result.concat(matrix[0]);
result.push(matrix[1][1], matrix[1][0]);
return result;
}
if (len > 2) {
// right
result.concat(matrix[0]);
// down
for (var j=1; j < matrix.length - 1; j++) {
result.push(matrix[j][matrix.length -1]);
}
// left
for (var l=matrix.length - 2; l > 0; l--) {
result.push(matrix[matrix.length - 1][l]);
}
// up
for (var k=matrix.length -2; k > 0; k--) {
result.push(matrix[k][0]);
}
}
// reset matrix for next loop
var temp = matrix.slice();
temp.shift();
temp.pop();
for (var i=0; i < temp.length - 1; i++) {
temp[i] = temp[i].slice(1,-1);
}
goAround(temp);
};
goAround(matriks);
};
🌀 Spiral Array (ES6)
ES6 allows us to keep it simple:
function spiral(matrix) {
const arr = [];
while (matrix.length) {
arr.push(
...matrix.shift(),
...matrix.map(a => a.pop()),
...(matrix.pop() || []).reverse(),
...matrix.map(a => a.shift()).reverse()
);
}
return arr;
}
Your code is very close but it is doing more than it needs to do. Here I simplify and bug fix:
var input = [[1, 2, 3, 4],
[5, 6, 7, 8],
[9, 10, 11, 12],
[13, 14, 15, 16]];
var spiralTraversal = function(matriks){
var result = [];
var goAround = function(matrix) {
if (matrix.length == 0) {
return;
}
// right
result = result.concat(matrix.shift());
// down
for (var j=1; j < matrix.length - 1; j++) {
result.push(matrix[j].pop());
}
// bottom
result = result.concat(matrix.pop().reverse());
// up
for (var k=matrix.length -2; k > 0; k--) {
result.push(matrix[k].shift());
}
return goAround(matrix);
};
goAround(matriks);
return result;
};
var result = spiralTraversal(input);
console.log('result', result);
Running it outputs:
result [1, 2, 3, 4, 12, 16, 15, 14, 13, 5, 6, 7, 8, 11, 10, 9]
JSFiddle: http://jsfiddle.net/eb34fu5z/
Important things:
concat on Array returns the result -- it does not mutate the caller so you need to save the result of the concat like so: result = result.concat(otherArray)
check the terminating condition at top of recursive array
for each pass, do the expected (top, right, bottom, left)
return the result
Here is how I would do it but I would add error checking to verify the array has an equal number of "rows" and "columns". So assuming the input is valid, here we go:
var input = [[1, 2, 3, 4],
[5, 6, 7, 8],
[9, 10, 11, 12],
[13, 14, 15, 16]];
function run(input, result) {
if (input.length == 0) {
return result;
}
// add the first row to result
result = result.concat(input.shift());
// add the last element of each remaining row
input.forEach(function(rightEnd) {
result.push(rightEnd.pop());
});
// add the last row in reverse order
result = result.concat(input.pop().reverse());
// add the first element in each remaining row (going upwards)
var tmp = [];
input.forEach(function(leftEnd) {
tmp.push(leftEnd.shift());
});
result = result.concat(tmp.reverse());
return run(input, result);
}
var result = run(input, []);
console.log('result', result);
Which outputs:
result [1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11, 10]
The general idea is we know for each pass we need to do these things:
Add the first array in input
Add the last item from each remaining array in input
Add the last array in input
Add the first item from each remaining array in input
So if we do the recursion with doing that at each pass, we can accomplish the spiraling.
JSFiddle: http://jsfiddle.net/2v6k5uhd/
This solution is for any kind of matrix (m * n), not just square(m * m). Below example takes 5*4 matrix and prints in spiral format.
var matrix = [[1,2,3,4], [14,15,16,5], [13,20,17,6], [12,19,18,7], [11,10,9,8]];
var row = currentRow = matrix.length, column = currentColumn = matrix[0].length;
while(currentRow > row/2 ){
// traverse row forward
for(var i = (column - currentColumn); i < currentColumn ; i++) { console.log(matrix[row - currentRow][i]); }
// traverse column downward
for(var i = (row - currentRow + 1); i < currentRow ; i++) { console.log(matrix[i][currentColumn - 1]) }
// traverse row backward
for(var i = currentColumn - 1; i > (column - currentColumn) ; i--) { console.log(matrix[currentRow - 1][i - 1]); }
// traverse column upward
for(var i = currentRow - 1; i > (row - currentRow + 1) ; i--) { console.log(matrix[i - 1][column - currentColumn]) }
currentRow--;
currentColumn--;
}
Your algorithm seems fine, there is only one mistake There are a few things, some more hard to spot than others.
The concat method does not alter the array (like push does), but returns a new array that contains all the elements from the original array and the arguments. The result is not mutated.
To fix this, you could either
use result = result.concat(…);
make it an explicit loop where you do result.push(…) (like the down, left and up ones you already wrote) or
use result.push.apply(result, …) to push multiple values at once
Your "left" or "up" loop does miss one element, the bottom left one. Either when going left, you need advance to the first element (use >= 0 in the condition), or when going up you will need to start in the last instead of the second-to-last row (matrix.length-1)
In the loop that shrinks the matrix for the next iteration you forgot the last row, it needs to be for (var i=0; i < temp.length; i++) (not temp.length-1). Otherwise you get very unfortunate results.
Your base case should be 0 (and 1), not (1 and) 2. This will both simplify your script and avoid errors (in edge cases).
You expect your matrices to be square, but they could be rectangular (or even have lines of uneven length). The .length you are accessing might be not the one you expect - better doublecheck and throw an error with a descriptive message.
Both spiralTraversal and goAround are missing a return statement for the (recursive) call. They just fill up result but don't return anything.
Recursive Solution:
Instead of going around, I just go over the top row, and the rightmost column, then recursively call the function on the "reversed" matrix.
var input = [
[ 1, 2, 3, 4],
[ 5, 6, 7, 8],
[ 9,10,11,12],
[13,14,15,16]
];
let spiral = (mat) => {
if(mat.length && mat[0].length) {
mat[0].forEach(entry => { console.log(entry)})
mat.shift();
mat.forEach(item => {
console.log(item.pop())
});
spiral(reverseMatrix(mat))
}
return;
}
let reverseMatrix = (mat) => {
mat.forEach(item => {
item.reverse()
});
mat.reverse();
return mat;
}
console.log("Clockwise Order is:")
spiral(input)
Here my function :
let array_masalah = [
[1,2,3,4],
[5,6,7,8],
[9, 10, 11, 12],
[13, 14, 15,16],
];
let array_masalah_2 = [
[1, 2, 3, 4, 5],
[6, 7, 8, 9, 10],
[11, 12, 13, 14, 15],
[16, 17, 18, 19, 20],
];
function polaSpiral(array_masalah) {
function spiral(array) {
if (array.length == 1) {
return array[0];
}
var firstRow = array[0]
, numRows = array.length
, nextMatrix = []
, newRow
, rowIdx
, colIdx = array[1].length - 1
for (colIdx; colIdx >= 0; colIdx--) {
newRow = [];
for (rowIdx = 1; rowIdx < numRows; rowIdx++) {
newRow.push(array[rowIdx][colIdx]);
}
nextMatrix.push(newRow);
}
firstRow.push.apply(firstRow, spiral(nextMatrix));
return firstRow
}
console.log(spiral(array_masalah));
}
polaSpiral(array_masalah) // [ 1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11, 10 ]
polaSpiral(array_masalah_2) // [ 1, 2, 3, 4, 5, 10, 15, 20, 19, 18, 17, 16, 11, 6, 7, 8, 9, 14, 13, 12 ]
While not recursive, it at least outputs the correct answer of:
result: [ 1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11, 10 ]
I'd say the only weird thing about this is having to "reset" the variables i,j after each while loop. Also, there's probably a cleaner recursive solution.
var array = [
[1, 2, 3, 4],
[5, 6, 7, 8],
[9, 10, 11, 12],
[13, 14, 15, 16]
];
function spiralTraversal(array) {
let discovered = new Set();
let result = [];
let totalSpots = array.length * array[0].length;
let direction = 'right';
for (var i = 0; i < array.length; i ++) {
for (var j = 0; j < array[i].length; j++) {
while (totalSpots) {
while (direction === 'right' && !!bounds(array, i, j) && !discovered.has(array[i][j])) {
discovered.add(array[i][j]);
result.push(array[i][j]);
totalSpots--;
j++;
}
direction = 'down';
i++;
j--;
while (direction === 'down' && !!bounds(array,i, j) && !discovered.has(array[i][i])) {
discovered.add(array[i][j]);
result.push(array[i][j]);
totalSpots--;
i++;
}
direction = 'left';
j--;
i--;
while (direction === 'left' && !!bounds(array, i, j) && !discovered.has(array[i][j])) {
discovered.add(array[i][j]);
result.push(array[i][j]);
totalSpots--;
j--;
}
direction = 'up';
i--;
j++
while (direction === 'up' && bounds(array, i, j) && !discovered.has(array[i][j])) {
discovered.add(array[i][j]);
result.push(array[i][j]);
totalSpots--;
i--;
}
direction = 'right';
j++;
i++;
}
}
}
return result;
}
function bounds(array, i, j){
if (i < array.length && i >= 0 && j < array[0].length && j >= 0) {
return true;
} else {
return false;
}
};
const spiralOrder = matrix => {
if (!matrix || matrix.length === 0) {
return [];
}
let startRow = 0;
let startCol = 0;
let ans = [];
let endCol = matrix[0].length - 1;
let endRow = matrix.length - 1;
while (startRow <= endRow && startCol <= endCol) {
for (let i = startCol; i <= endCol; i++) {
ans.push(matrix[startRow][i]);
}
startRow++;
for (let i = startRow; i <= endRow; i++) {
ans.push(matrix[i][endCol]);
}
endCol--;
if (startRow <= endRow) {
for (let i = endCol; i >= startCol; i--) {
ans.push(matrix[endRow][i]);
}
endRow--;
}
if (startCol <= endCol) {
for (let i = endRow; i >= startRow; i--) {
ans.push(matrix[i][startCol]);
}
startCol++;
}
}
return ans;
};
let input = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
//Output: [1, 2, 3, 6, 9, 8, 7, 4, 5];
spiralOrder(input);
Below is a Javascript solution. I have added comments to the code so you can follow along with the process :)
var array = [
[1, 2, 3, 4],
[5, 6, 7, 8],
[9, 10, 11, 12],
[13, 14, 15, 16]
];
var n = array.length;
//create empty 2d array
var startRow = 0;
var endRow = n - 1;
var startColumn = 0;
var endColumn = n - 1
var newArray = [];
// While loop is used to spiral into the 2d array.
while(startRow <= endRow && startColumn <= endColumn) {
// Reading top row, from left to right
for(var i = startColumn; i <= endColumn; i++) {
newArray.push(array[startColumn][i]);
}
startRow++; // Top row read.
// Reading right column from top right to bottom right
for(var i = startRow; i <= endRow; i++) {
newArray.push(array[i][endColumn]);
}
endColumn--; // Right column read
// Reading bottom row, from bottom right to bottom left
for(var i = endColumn; i >= startColumn; i--) {
newArray.push(array[endRow][i]);
}
endRow--; // Bottom row read
// Reading left column, from bottom left to top left
for(var i = endRow; i >= startRow; i--) {
newArray.push(array[i][startColumn]);
}
startColumn++; // left column now read.
} // While loop will now spiral in the matrix.
console.log(newArray);
:)
ES6 JS version with clockwise and anticlockwise spiral traversal.
function traverseSpiral(arr2d,directionMap,initialPos){
// Initializing length.
const len = arr2d.length;
let totalElementsTraversed =0;
// Elements in the first line is equal to the array length.
// (as this is a square matrix)
let elementsInLine=len;
let elementsTraversedInRow = 0;
let linesCompleted = 1;
let direction = initialPos[0] === 0 ? 'r' : 'd';
// Function to move in the desired direction.
const move = checkDirectionAndMove(initialPos);
const spiralArray = [];
while( totalElementsTraversed!==len*len){
// On Each line completion
if(elementsTraversedInRow===elementsInLine){
linesCompleted++;
// Reset elements traversed in the row.
elementsTraversedInRow =0;
// After each line completion change direction.
direction = directionMap.get(direction);
// For every 2 traversed lines elements in the line will decrease.
if(linesCompleted % 2===0) elementsInLine--;
}
// Update elements traversed
totalElementsTraversed+=1
elementsTraversedInRow+=1;
// Move in the defined direction
const [ down,right] = move(direction);
spiralArray.push(arr2d[down][right]);
}
return spiralArray;
}
function checkDirectionAndMove(initialPosition) {
// Unpack array to variables
let [down,right] = initialPosition;
// Return function.
return (direction)=> {
// Switch based on right/left/up/down direction.
switch(direction){
case 'r':
right++;
break;
case 'l':
right--;
break;
case 'd':
down++;
break;
default :
down--;
}
return [down,right]
}
}
// If current direction is right move down and so on....
const clockWiseMap = new Map(Object.entries({
'r':'d',
'd':'l',
'l':'u',
'u':'r'
}));
// If current direction is right move up and so on....
const antiClockWiseMap = new Map(Object.entries({
'r':'u',
'd':'r',
'l':'d',
'u':'l'
}));
// Spiral traversal in the clockwise direction.
const clockWiseSpiralTraversal = traverseSpiral(
[[1, 2, 3, 4, 5],
[16, 17, 18, 19, 6],
[15, 24, 25, 20, 7],
[14, 23, 22, 21, 8],
[13, 12, 11, 10, 9]],
clockWiseMap,
[0,-1]
)
// Spiral traversal in the anti-clockwise direction.
const antiClockWiseSpiralTraversal = traverseSpiral(
[[1, 2, 3, 4, 5],
[16, 17, 18, 19, 6],
[15, 24, 25, 20, 7],
[14, 23, 22, 21, 8],
[13, 12, 11, 10, 9]],
antiClockWiseMap,
[-1,0]
)
console.log("Clock wise traversal :", clockWiseSpiralTraversal)
console.log("Anti-clock wise traversal :",antiClockWiseSpiralTraversal)
Returns :
Clock wise traversal : [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 ]
Anti-clock wise traversal : [ 1, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 17, 24, 23, 22, 21, 20, 19, 18, 25 ]
Main used techniques and others:
Closure, Arrow functions,
Higher-order functions, Conditional/ternary operator, Array destructuring,
and JS map.
I'm use to C#:
public static IList<int> spiralTraversal (int[,] matrix)
{
IList<int> list = new List<int>();
// Get all bounds before looping.
int bound0 = matrix.GetUpperBound(0);
int bound1 = matrix.GetUpperBound(1);
int totalElem = (bound0+1) * (bound1+1);
int auxbound0 = 0;
int auxbound1 = 0;
string direction = "left";
int leftCtrl = 0;
int rightCtrl = 0;
int upCtrl = 0;
int downCtrl = 0;
for (int i=0;i< totalElem;i++)
{
if (direction == "down")
{
list.Add(matrix[auxbound0, auxbound1]);
if (auxbound0 == bound0 - downCtrl)
{
direction = "right";
auxbound1 -= 1;
downCtrl += 1;
continue;
}
else
{
auxbound0 += 1;
}
}
if (direction == "left")
{
list.Add(matrix[auxbound0, auxbound1]);
if (auxbound1 == bound1 - leftCtrl)
{
direction = "down";
auxbound0 += 1;
leftCtrl += 1;
continue;
}
else
{
auxbound1 += 1;
}
}
if (direction == "up")
{
list.Add(matrix[auxbound0, auxbound1]);
if (auxbound0 == 1 + upCtrl)
{
direction = "left";
auxbound1 += 1;
upCtrl += 1;
continue;
}
else
{
auxbound0 -= 1;
}
}
if (direction == "right")
{
list.Add(matrix[auxbound0, auxbound1]);
if (auxbound1 == rightCtrl)
{
direction = "up";
auxbound0 -= 1;
rightCtrl += 1;
continue;
}
else
{
auxbound1 -= 1;
}
}
}
return list;
}
This solution takes spiral array and converts it to Ordered Array.
It Sorts Spiral Matrix with the format of Top, Right, Bottom, Left.
const matrix = [
[1, 2, 3, 4, 5],
[16, 17, 18, 19, 6],
[15, 24, 25, 20, 7],
[14, 23, 22, 21, 8],
[13, 12, 11, 10, 9],
];
function getOrderdMatrix(matrix, OrderdCorner) {
// If the Matrix is 0 return the OrderdCorner
if (matrix.length > 0) {
//Pushes the top of the matrix to OrderdCorner array
OrderdCorner.push(...matrix.shift());
let left = [];
/*Pushes right elements to the Orderdcorner array and
Add the left elements to the left array */
for (let i = 0; i < matrix.length; i++) {
OrderdCorner.push(matrix[i][matrix[i].length - 1])
matrix[i].pop(); //Remove Right element
if (matrix[i].length > 0) {
//Starts from the last element of the left corner
left.push(matrix[(matrix.length - 1) - i][0])
matrix[(matrix.length - 1) - i].shift();
}
}
/* If the array length is grater than 0 add the bottom
to the OrderdCorner array */
if (matrix.length > 0) {
OrderdCorner.push(...matrix.pop().reverse());
}
//Ads the left array to the OrderdCorner array
OrderdCorner.push(...left);
return getOrderdMatrix(matrix, OrderdCorner);
} else {
return OrderdCorner
}
}
console.log(getOrderdMatrix(matrix,[]));
Returns
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25]
Here's a configurable version :
function spiral(n) {
// Create 2D array of size n*n
var matrix = new Array(n);
for(var i=0; i < matrix.length; i++) {
matrix[i] = new Array(n);
}
for(var i=0; i < n;i++) {
for(var j=0; j < n; j++) {
matrix[i][j] = 0;
}
}
var startNum = 0;
var rowNum = 0;
function spin(rowNum) {
// right
for(var j=rowNum; j < (n-rowNum); j++) {
startNum++;
matrix[rowNum][j] = startNum;
}
if(startNum === (n*n)) {
return; // exit if number matches to the size of the matrix. ( 16 = 4*4 )
}
// down
for(var i=(rowNum+1); i < (n-(rowNum+1)); i++) {
startNum++;
matrix[i][n-(rowNum+1)] = startNum;
}
if(startNum === (n*n)) {
return; // exit if number matches to the size of the matrix. ( 16 = 4*4 )
}
// left
for(var j=(n-(1+rowNum)); j >= rowNum; j--) {
startNum++;
matrix[(n-(1+rowNum))][j] = startNum;
}
if(startNum === (n*n)) {
return; // exit if number matches to the size of the matrix. ( 16 = 4*4 )
}
//top
for(var i=(n-(2+rowNum)); i > rowNum; i--) {
startNum++;
matrix[i][rowNum] = startNum;
}
if(startNum === (n*n)) {
return; // exit if number matches to the size of the matrix. ( 16 = 4*4 )
}
spin(rowNum+1);
}
spin(rowNum);
console.log(matrix)
}
spiral(6);
Example : https://jsfiddle.net/dino_myte/276ou5kb/1/
I have written an article for a while about this beautiful toy problem, I really enjoy it. you might need to check out my solution.
you can follow me on Medium and you can check my article from here.
var spiralTraversal = function (matrix, result = []) {
// TODO: Implement me!
// if the length of the matrix ==0 we will return the result
if (matrix.length == 0) {
return result;
}
// we need to push the elements inside the first element of the array then delete this element
while (matrix[0].length) {
result.push(matrix[0].shift());
}
//top right to bottom right
matrix.forEach((row) => {
result.push(row.pop());
});
//bottom right to bottom left
while (matrix[matrix.length - 1].length) {
result.push(matrix[matrix.length - 1].pop());
}
//reverse again so we can retraverse on the next iteration
matrix.reverse();
//filter out any empty arrays
matrix = matrix.filter((element) => element.length);
//recursive case
result = spiralTraversal(matrix, result);
//return the result and filter any undefined elements
return result.filter((element) => element);
};

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