Problem

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

You can return the answer in any order.

Constraints:

2 <= nums.length <= 105-109 <= nums[i] <= 109-109 <= target <= 109Only one valid answer exists.

Example1

Input: nums = [2,7,11,15], target = 9 Output: [0,1] Output: Because nums[0] + nums[1] == 9, we return [0, 1].

Example2

Input: nums = [3,2,4], target = 6 Output: [1,2]

Example3

Input: nums = [3,3], target = 6 Output: [0,1]

Solution

class Solution { public: vector<int> twoSum(vector<int>& nums, int target) { vector<int> ret; unordered_map<int,int> my_map; for(int i = 0;i<nums.size();++i) { int num_to_find = target - nums[i]; if(my_map.count(num_to_find)) { ret.push_back(i); ret.push_back(my_map[num_to_find]); return ret; } my_map[nums[i]] = i; } return ret; } };