twoSum.cpp

#include <iostream>
#include <vector>
#include <unordered_map>

// https://leetcode.com/problems/two-sum/

class Solution
{

public:
  std::vector<int> twoSum(std::vector<int> &nums, int target)
  {
    std::unordered_map<int, int> numberIndexMap;

    int numsSize = nums.size();

    for (int i = 0; i < numsSize; i += 1)
    {
      int num = nums[i];

      int rest = target - num;

      int numberNotExist = numberIndexMap.count(num) == 0;

      if (numberNotExist)
      {
        numberIndexMap[rest] = i;
      }
      else
      {
        std::vector<int> result{i, numberIndexMap[num]};
        return result;
      };
    }

    std::vector<int> result;

    return result;
  }
};