leetcode之 Array Partition I

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:

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].

题目本质上就是排序，取前n个的和

class Solution {
public:
    int arrayPairSum(vector<int>& nums) {
        if(nums.empty() || nums.size()%2 !=0)
            return 0;
        int sum =0;
        std::sort(nums.begin(), nums.end());
        for(int n=0;n<nums.size();n+=2)
        {
            sum = sum + nums[n];
        }
        return sum;
    }
};