1. Description

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.
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].

2. Runtime Distribution

3. Submission Details

4. Example

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).

5. Code

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public int arrayPairSum(int[] nums) {
	if (nums == null || nums.length == 0) {
		return 0;
	}
	Arrays.sort(nums);

	int result = 0;
	for (int i = 0; i < nums.length; i += 2) {
		result += nums[i];
	}
	return result;
}

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6.Test

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import java.util.Arrays;

public class LeetCode0561 {
	public int arrayPairSum(int[] nums) {
		if (nums == null || nums.length == 0) {
			return 0;
		}
		Arrays.sort(nums);

		int result = 0;
		for (int i = 0; i < nums.length; i += 2) {
			result += nums[i];
		}
		return result;
	}

	public static void main(String[] args) {
		LeetCode0561 leetcode = new LeetCode0561();
		int[] nums = new int[] { 1, 4, 3, 2 };
		System.out.println(leetcode.arrayPairSum(nums));
	}
}

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