Problem

Given an array of integers, return the indices of the two numbers such that they add up to a specific target.
Input: [2, 7, 11, 15], target = 9
Output: [0, 1]

Solution

// Solution:
// The optimal solution is to use a hash table to store the numbers in the array as keys and their indices as values.
// Then, we can iterate through the array and check if the target minus the current number is in the hash table.
// If it is, we return the indices of the current number and the target minus the current number.
// This solution is optimal because it has a time complexity of O(n) and a space complexity of O(n).

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

console.log(twoSum([2, 7, 11, 15], 9)); // [ 0, 1]
console.log(twoSum([3, 2, 4], 6)); // [1, 2]
console.log(twoSum([3, 3], 6)); // [0, 1]