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> res; unordered_map<int,int> mapping; for(size_t i=0;i<nums.size();i++){ mapping[nums[i]] = i; } for(size_t i=0;i<nums.size();i++){ const int key = target - nums[i]; if(mapping.find(key) != mapping.end()){ if(i != mapping[key]){ res.push_back(i); res.push_back(mapping[key]); break; } } } return res; } };
原文：http://www.cnblogs.com/wxquare/p/5921976.html