leetcode-【简单题】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.

样例：

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

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

答案：

简单遍历vector就行了，size*size复杂度，本来想先排序，再遍历，但是排序需要记录排序前和排序后索引的对应关系。

代码：

 #include <algorithm>

 class Solution {
 private:
    static bool cmp(const int &a, const int &b)
    {
        return a < b;
    }

 public:
     vector<int> twoSum(vector<int>& nums, int target) {
        // std::sort(nums.begin(),nums.end(),cmp);

         int i,j;
         int size = nums.size();
         int rest;
         vector<int> ans;

         for(i = ; i < size; ++ i)
         {
             rest = target - nums[i];
             for(j = i + ;j < size; ++ j)
             {
                 if(rest == nums[j])
                 {
                     ans.push_back(i);
                     ans.push_back(j);
                     return ans;
                 }
             }
         }
     }
 };