561. Array Partition I

Question:

Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), ..., (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as possible. 

Example 1:

Input: [1,4,3,2]

Output: 4
Explanation: n is 2, and the maximum sum of pairs is 4.

Note:

1. n is a positive integer, which is in the range of [1, 10000].
2. All the integers in the array will be in the range of [-10000, 10000].

Solution:

class Solution {
public:
    int arrayPairSum(vector<int>& nums) {
        vector<int>::size_type nsize=nums.size();//计算数组大小
        if(nsize==0){//如果大小为0，直接返回0
            return 0;
        }
        sort(nums.begin(),nums.end());//排序
        int sum=0;
        for(int i=0;i<nsize;i+=2){//计算两两一组中，数小的那个，和即为结果
            sum+=nums[i];
        }
        return sum;
    }
};

题目直达：https://leetcode.com/problems/array-partition-i/

答案直达：http://www.itdadao.com/articles/c15a1321689p0.html