Coding Challenge Practice - Question 63

The task is to find two numbers that sum to 0 and return their indices, given an array of integers.

The boilerplate code:

function findTwo(arr) {
  // your code here
}

The array is scanned through once, while keeping track of every character seen

const map = new Map();

For each number x, check if -x has been seen before. If yes, return both indices.

for(let i = 0; i < arr.length; i++) {
    const complement = -arr[i];
    if(map.has(complement)) {
      return [map.get(complement), i];
    }
    map.set(arr[i], i)
  }

If no pairs sum to 0, return null.

The final code

function findTwo(arr) {
  // your code here
  const map = new Map();

  for(let i = 0; i < arr.length; i++) {
    const complement = -arr[i];
    if(map.has(complement)) {
      return [map.get(complement), i];
    }
    map.set(arr[i], i)
  }
  return null;
}

That's all folks!