LeetCode题解:1.Two Sum

题目链接：

1. Two Sum

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题目描述：

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.

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

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

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题目解释：

给定一个数组，里面存放着一组整数，然后给定一个目标整数，求在数组中的相加和为目标数的两个数的索引。

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解题方案：

这个题目其实比较简单，类似于一群人相互握手，握手的次数为：n * (n-1) / 2, 我们只要进行两层循环，尝试所有相加和组合即可。

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AC代码：

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {

      int len = nums.size();
      vector<int> res;

      for(int i = 0; i < len; i++) {
        for(int j = i + 1; j < len; j++) {
          if(nums[i] + nums[j] == target) {
        res.push_back(i);
        res.push_back(j);
          }
        }
      }

      return res;
    }

};