ArrayPartitionI.js

//https://leetcode.com/problems/array-partition-i/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.

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

/* Solution */

/**
 * @param {number[]} nums
 * @return {number}
 */
var arrayPairSum = function(nums) {
	var sum = 0 ;

	//sort nums
    function sortNum(a,b) {
	    return a - b;
	}
    nums.sort(sortNum);
    //sum[0]+sum[2]+sum[4]+...
    for(var i = 0;i < nums.length - 1;i += 2) {
        sum += nums[i];
    }
  return sum;
};