array-partition.java

// Given an integer array nums of 2n integers, group these integers into n pairs (a1, b1), (a2, b2), ..., (an, bn) such that the sum of min(ai, bi) for all i is maximized. Return the maximized sum.
//
//  
// Example 1:
//
//
// Input: nums = [1,4,3,2]
// Output: 4
// Explanation: All possible pairings (ignoring the ordering of elements) are:
// 1. (1, 4), (2, 3) -> min(1, 4) + min(2, 3) = 1 + 2 = 3
// 2. (1, 3), (2, 4) -> min(1, 3) + min(2, 4) = 1 + 2 = 3
// 3. (1, 2), (3, 4) -> min(1, 2) + min(3, 4) = 1 + 3 = 4
// So the maximum possible sum is 4.
//
// Example 2:
//
//
// Input: nums = [6,2,6,5,1,2]
// Output: 9
// Explanation: The optimal pairing is (2, 1), (2, 5), (6, 6). min(2, 1) + min(2, 5) + min(6, 6) = 1 + 2 + 6 = 9.
//
//
//  
// Constraints:
//
//
// 	1 <= n <= 104
// 	nums.length == 2 * n
// 	-104 <= nums[i] <= 104
//
//


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