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Ways to get to a specific sum in JavaScript
Problem
We are required to write a JavaScript function that takes in an array of Integers, arr, as the first argument and a single integer, target, as the second argument.
For each Integer in the array, our function can either assign ‘+’ or ‘-’ to it.
Our function should find out how many ways in total exist to assign ‘+’, ‘-’ to make the sum of integers of the array equal to the target sum, target.
For example, if the input to the function is −
const arr = [1, 1, 1, 1, 1]; const target = 3;
Then the output should be −
const output = 5;
Output Explanation:
Because the 5 ways are −
-1+1+1+1+1 = 3 +1-1+1+1+1 = 3 +1+1-1+1+1 = 3 +1+1+1-1+1 = 3 +1+1+1+1-1 = 3
Example
The code for this will be −
const arr = [1, 1, 1, 1, 1];
const target = 3;
const waysToSum = (arr = [], target = 1) => {
const map = {};
const find = (arr, target, i) => {
let val = i + '->' + target;
if(map[val] !== undefined){
return map[val];
};
if(i === 0){
if (target === 0 && arr[0] === 0) { return 2 }
return arr[0] === target || arr[0] === -target ? 1 : 0
};
map[val] = find(arr, target + arr[i], i - 1) + find(arr, target - arr[i], i - 1);
return map[val]
};
return find(arr, target, arr.length-1)
};
console.log(waysToSum(arr, target));Output
And the output in the console will be −
5
Updated on: 04-Mar-2021
62 Views
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