recursion
hackerrank.com/challenges/the-power-sum/problem
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| function powerSum(x, n, i=1) {
const num = Math.pow(i, n);
if(num<x) {
return powerSum(x, n, i+1) + powerSum(x-num, n, i+1);
} else if(num === x) {
return 1;
} else {
return 0;
}
}
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https://www.hackerrank.com/challenges/recursive-digit-sum/problem
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| function superDigit(n, k=1) {
if(n<10) {
return n;
}
return superDigit(k*String(n).split('').reduce((acc, val) => acc+Number.parseInt(val), 0), 1);
}
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combinations
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| const coins=[1,5,10,50];
function combination(num,coins) {
const result = [];
function combinehelper(num, indexofcoins, temp=[]) {
let combine=[...temp];
if(indexofcoins<coins.length ){
if( num<0){
combine.pop()
}
else if(num===0){
result.push(combine);
}
else if(num>0){
combine.push(coins[indexofcoins]);
combinehelper(num-coins[indexofcoins],indexofcoins, combine);
combinehelper(num,indexofcoins+1, temp);
}
}
}
combinehelper(num, 0, temp);
return result;
}
console.log(combination(11,coins))
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https://algodaily.com/challenges/the-coin-change-problem
https://gist.github.com/jeanlauliac/8674996
https://www.codewars.com/kata/54d81488b981293527000c8f/javascript
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| const sumPairs = (ints, s) => {
if (ints.length < 2) {
return undefined;
}
let set = new Set();
set.add(ints[0]);
for (let i=1; i < ints.length; i++) {
let checkedNum = s-ints[i];
if (set.has(checkedNum)) {
return [checkedNum,ints[i]];
}
set.add(ints[i]);
}
return undefined;
}
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