Check for Subarray with 0 Sum in JavaScript

We are required to write a JavaScript function that takes in an array of Numbers with some positive and negative values. We are required to determine whether there exists a subarray in the original array whose net sum is 0 or not.

Our function should return a boolean on this basis.

Approach

The approach here is simple. We iterate over the array using a for loop, calculate the cumulative sum up to that particular element. And if any point the cumulative becomes 0 or attains a value it has previously attained, then there exists a subarray with sum 0. Otherwise there exists no subarray with sum 0.

Therefore, let's write the code for this function −

Example

const arr = [4, 2, -1, 5, -2, -1, -2, -1, 4, -1, 5, -2, 3];
const zeroSum = arr => {
   const map = new Map();
   let sum = 0;
   for(let i = 0; i < arr.length; i++){
      sum += arr[i];
      if(sum === 0 || map.get(sum)){
         return true;
      };
      map.set(sum, i);
   };
   return false;
};
console.log(zeroSum(arr));

Output

The output in the console will be −

true