Make a recursive function in JavaScript [closed] - javascript

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I am trying to make a recursive function for this parameters. Function should determine the nth element of the row
a_0 = 1
a_k = k*a_(k-1) + 1/k
k = 1,2,3...
I am trying really hard to do this but i cant get a result. Please help me to do this
I came up with this but it is not a recursive function. I can not do this as a recursive function
let a = 1
let k = 1
let n = 3
for (let i = 1; i<=n; i++){
a = i*a + 1/i
}
console.log(a)

Here's the recursive function you're looking for, it has two conditions:
k == 0 => 1
k != 0 => k * fn(k - 1) + 1/k
function fn(k) {
if(k <= 0) return 1;
return k * fn(k - 1) + 1/k;
}
console.log(fn(1));
console.log(fn(2));
console.log(fn(3));
console.log(fn(4));
Note: I changed the condition of k == 0 to k <= 0 in the actual function so it won't stuck in an infinite loop if you pass a negative k

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Check numbers in a range that contain or are divisible by 7 [closed]

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I don't know what is the problem with this code I just need to know
how many number from Start to end that divide by 7 or has 7.
const divideOrHasSeven = (start, end) => {
var x = 0;
for (i = start; i <= end; i++) {
if (i % 7 || i.toString().indexOf("7")) { // if it is divide by 7 or has 7
x += 1;
}
}
return x;
};
The problem is i.toString().indexOf('7') will always return a truthy value EXCEPT (ironically) when 7 is actually in the number (inthe first position - index zero)
Change your conditional to if (i%7===0 || i.toString().indexOf('7')>-1)
You had some problems with your code.
If you compare with this, I think you will understand where.
This i.toString().indexOf('7') will return -1 if 7 is not found in string, which will be evaluated as true.
You also had some syntax errors.
const divideOrHasSeven = (start, end) => {
var x = 0;
for (i = start; i <= end; i++) {
if (i%7 === 0 || i.toString().indexOf('7') >= 0) {
x += 1;
}
}
return x
}
console.log(divideOrHasSeven(1, 200));

How can loop be rewritten as anonymous function? [closed]

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how can this type of loop be overwritten
let num - fieldOffset[0];
for (let i = 1; i < fieldOffset.length; i++) {
if (fieldOffset[i] < fieldOffset[i - 1]) {
num += fieldOffset[i];
}
}
as an anonymous function of the following type:
const reducer = (accumulator, currentValue) => accumulator + currentValue;
array1.reduce(reducer)
Using the third (optional) argument of Array.prototype.reduce should do the trick:
num = fieldOffset.reduce((acc, value, index) => acc += (index && (value > fieldOffset[index - 1])) ? value : 0, 0);

Calculating trailing zero in javascript [closed]

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How do i calculate the number of trailing zeros in a factorial of a given number.
N! = 1 * 2 * 3 * 4 ... N
Any Help on this?
Because zeros come from factors 5 and 2 being multiplied together, iterate over all numbers from 1 to the input number, adding to a cumulative count of fives and twos whenever those factors are found. Then, return the smaller of those two counts:
function zeroCount(n) {
let fives = 0;
let twos = 0;
for (let counter = 2; counter <= n; counter++) {
let n = counter;
while (n % 2 === 0) {
n /= 2;
twos++;
}
while (n % 5 === 0) {
n /= 5;
fives++;
}
}
return Math.min(fives, twos);
}
console.log(zeroCount(6)); // 720
console.log(zeroCount(10)); // 3628800
It is very simple, This will help you.
function TrailingZero(n)
{
var c = 0;
for (var i = 5; n / i >= 1; i *= 5)
c += parseInt(n / i);
return c;
}
Let me know if you need help to understand this function.

Find extra character between two strings [closed]

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How can I find an extra character between two strings in an optimal way.
Ex1: S1 - 'abcd', S2 - 'abcxd', output - 'x'
Ex2: S1 - '100001', S2 - '1000011', output - '1'
We can do this by traversing linearly and comparing each character in O(n). I want this to be done in much more optimal way, say in O(logn)
Baseline method (O(n)): Just comparing chars and narrowing in on both sides each cycle.
function findDiffChar(base, baseExtraChar) {
let extraLastIndex = base.length;
let lastIndex = extraLastIndex - 1;
for (let i = 0; i < extraLastIndex / 2; i++) {
console.log(`Loop: ${i}`);
if (base[i] !== baseExtraChar[i])
return baseExtraChar[i];
if (base[lastIndex - i] !== baseExtraChar[extraLastIndex - i])
return baseExtraChar[extraLastIndex - i];
}
return false;
}
console.log(findDiffChar('FOOOOOAR', 'FOOOOOBAR')); // B
Improved method using binary search (O(log n)): Compare halves until you've narrowed it down to one character.
function findDiffChar(base, baseExtraChar) {
if (baseExtraChar.length === 1) return baseExtraChar.charAt(0);
let halfBaseLen = Number.parseInt(base.length / 2) || 1;
let halfBase = base.substring(0,halfBaseLen);
let halfBaseExtra = baseExtraChar.substring(0,halfBaseLen);
return (halfBase !== halfBaseExtra)
? findDiffChar(halfBase, halfBaseExtra)
: findDiffChar(base.substring(halfBaseLen),baseExtraChar.substring(halfBaseLen));
}
console.log(findDiffChar('FOOOOAR', 'FOOOOBAR')); // B
console.log(findDiffChar('---------', '--------X')); // X
console.log(findDiffChar('-----------', '-----X-----')); // X
console.log(findDiffChar('------------', '---X--------')); // X
console.log(findDiffChar('----------', '-X--------')); // X
console.log(findDiffChar('----------', 'X---------')); // X

Matlab point in polygon [closed]

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Hi found this code on this list and need help converting it to Matlab.
int pnpoly(int nvert, float *vertx, float *verty, float testx, float testy)
{
int i, j, c = 0;
for (i = 0, j = nvert-1; i < nvert; j = i++) {
if ( ((verty[i]>testy) != (verty[j]>testy)) &&
(testx < (vertx[j]-vertx[i]) * (testy-verty[i]) / (verty[j]-verty[i]) + vertx[i]) )
c = !c;
}
return c;
}
nvert: Number of vertices in the polygon. Whether to repeat the first vertex at the end.
vertx, verty: Arrays containing the x- and y-coordinates of the polygon's vertices.
testx, testy: X- and y-coordinate of the test point. (This is from another Stack Overflow question: Point in Polygon aka hit test.
JavaScript version:
function insidePoly(poly, pointx, pointy) {
var i, j;
var inside = false;
for (i = 0, j = poly.length - 1; i < poly.length; j = i++) {
if(((poly[i].y > pointy) != (poly[j].y > pointy)) && (pointx < (poly[j].x-poly[i].x) * (pointy-poly[i].y) / (poly[j].y-poly[i].y) + poly[i].x) ) inside = !inside;
}
return inside;
}
How will this translate in Matlab:
function insidePoly = inpoly(poly, pointx, pointy)
% Code
% return inside
Matlab comes with a build-in function inpolygon which seems to do exactly what you are asking for. No need to reimplement it.

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