LeetCode 1. Two Sum: CPP Solution

Problem Statement

---

Given an integer array of size N, return indices of the two numbers such that they add up to a specific target.

Function Signature:
  C++
    vector<int> twoSum(vector<int> input, int target) {...}

Inputs:
  input = [2, 4, 6, 7]
  target = 9,

Outputs:
  [0, 3]
     (because input[0] + input[3] = 2 + 7 = 9)

Solution: Hash Table

---

vector<int> twoSum(vector<int>& nums, int target) {
    unordered_map<int, int> map;
    for (int i = 0; i < nums.size(); i++) {
        if (map.find(nums[i]) != map.end()) {
            vector<int> result = {map[nums[i]], i};
            return result;
        }
        else {
            map[target - nums[i]] = i;
        }
    }
}

A thorough writeup of this solution can be found here.