class Solution { public: vector twoSum(vector& nums, int target) { unordered_map numToIndex; vector ans(2); for (int i = 0; i < nums.size(); i++) { int complement = target - nums[i]; if (numToIndex.find(complement) != numToIndex.end()) { ans[0] = numToIndex[complement]; ans[1] = i; } numToIndex[nums[i]] = i; } return ans; } };