561. Array Partition I（python+cpp）

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题目：

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 = min(1, 2) + min(3, 4). Note: n is a positive integer, which is in the range of [1, 10000]. All the integers in the array will be in the range of [-10000, 10000].

解释：
先对列表排序，然后按顺序每次取出两个min一下求和~

python代码：

class Solution(object):
    def arrayPairSum(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        return sum(sorted(nums)[::2])

c++代码：

#include <algorithm>
class Solution {
public:
    int arrayPairSum(vector<int>& nums) {
        sort(nums.begin(),nums.end());
        int result=0;
        for(int i=0;i<nums.size();i+=2)
            result+=nums[i];
        return result;
            
    }
};

总结：
#include <algorithm>里面的sort()函数。