LeetCode1. Two Sum

题目：

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, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,Because nums[0] + nums[1] = 2 + 7 = 9,return [0, 1].

题目分析：

这道题用STL中的map可以很简单地解决问题，属于简单题，在这里就不在多做分析了。

用unorderedmap可以减少时间复杂度。

代码：

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