1. Two Sum

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

You may assume that each input would have exactly one solution.

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

UPDATE (2016/2/13):
The return format had been changed to zero-based indices. Please read the above updated description carefully.

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