Problem

Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

Solution

// Solution:
// The optimal solution is to use a hash table to store the numbers and their indices.
// This way, we can check if the complement of the current number is in the hash table.
// If it is, we can return the indices of the current number and the complement.
// This solution is optimal because it is O(n) time complexity and O(n) space complexity.

const twoSum = (nums, target) => {
  const hashTable = {};
  for (let i = 0; i < nums.length; i++) {
    const complement = target - nums[i];
    if (hashTable[complement] !== undefined) {
      return [hashTable[complement], i];
    }
    hashTable[nums[i]] = i;
  }
};

console.log(twoSum([2, 7, 11, 15], 9));