561. Array Partition I

Solution Code

C#

public class Solution {
    public int ArrayPairSum(int[] nums) {
        int n = nums.Length, answer = 0;
        Array.Sort(nums);
        
        for (int i = 0; i < n; i += 2)
            answer += nums[i];
        
        return answer;
    }
}

C++

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

Java

class Solution {
    public int arrayPairSum(int[] nums) {
        int n = nums.length, answer = 0;
        Arrays.sort(nums);
        
        for (int i = 0; i < n; i += 2)
            answer += nums[i];
        
        return answer;
    }
}

Python

class Solution(object):
    def arrayPairSum(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        nums.sort()
        return sum([i for i in nums[::2]])

Ruby

# @param {Integer[]} nums
# @return {Integer}
def array_pair_sum(nums)
    nums.sort!
    (nums.select!.with_index { |_,i| i.even? }).sum
end

Resources

Editorial Series - LeetCode 561. Array Partition I