1. Two Sum.cpp

class Solution {
 public:
  vector<int> twoSum(vector<int>& nums, int target) {
    unordered_map<int, int> numToIndex;

    for (int i = 0; i < nums.size(); ++i) {
      if (const auto it = numToIndex.find(target - nums[i]);
          it != cend(numToIndex))
        return {it->second, i};
      numToIndex[nums[i]] = i;
    }
  throw;
  }
};