Crushing Job Interviews(DSA) – Two Number Sum

The Query

Issue: Straightforward

Write a perform that takes in a non-empty array of distinct integers and an integer representing a goal sum. If any two numbers within the enter array sum as much as the goal sum, the perform ought to return them in an array, in any order. If no two numbers sum as much as the goal sum, the perform ought to return an empty array.

Be aware that the goal sum must be obtained by summing two completely different integers within the array; you may’t add a single integer to itself to be able to get hold of the goal sum.

You’ll be able to assume that there will likely be at most one pair of numbers summing as much as the goal sum.

Pattern Enter

array = [3, 5, -4, 8, 11, 1, -1, 6]
targetSum = 10

Pattern Output

[-1, 11] // the numbers could possibly be in reverse order

Optimum Area & Time Complexity:

O(n) time | O(n) area – the place n is the size of the enter array

The Considering

When you paid consideration to the boring maths professor’s class, you would possibly be capable of give you this options very simply.

So let’s imagine

// 10 is the goal sum
10 = x + y
// so
y = 10 - x

P.S: Hashmap is only a object in javascript or dictionary in python.

So now what we do is, we create a hashmap and iterate via the array that is given to us. Then we:

  • examine if the hash has y ie 10 - x
  • if the worth is there, then we return the array, since we’ve got each x and y
  • if not then we add that num to the hashmap

The Resolution

perform twoNumberSum(array, targetSum) {
    const nums = {} // that is the hashmap

  for (let num of array){
    if (nums[targetSum - num] ) return [targetSum-num, num]
    nums[num] = true

  return []

// Don't edit the road under.
exports.twoNumberSum = twoNumberSum;

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