// Source : https://leetcode.com/problems/array-partition-i
// Author : Dean Shi
// Date   : 2017-04-23

/***************************************************************************************
 *
 * 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:
 *
 * 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].
 *
 *
 ***************************************************************************************/

/**
 * @param {number[]} nums
 * @return {number}
 */
var arrayPairSum = function(nums) {
    return nums.sort((a, b) => b - a).reduce((sum, v, i) => sum += i % 2 ? v : 0, 0)
};

// Source : https://leetcode.com/problems/array-partition-i
// Author : Dean Shi
// Date   : 2017-04-23

/***************************************************************************************
 *
 * 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:
 *
 * 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].
 *
 *
 ***************************************************************************************/

/**
 * @param {number[]} nums
 * @return {number}
 */
var arrayPairSum = function(nums) {
    return nums.sort((a, b) => b - a).reduce((sum, v, i) => sum + (i % 2 ? v : 0), 0)
};

Update ArrayPartition_I.js