Add solution #561

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,390 LeetCode solutions in JavaScript
+# 1,391 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -445,6 +445,7 @@
 558|[Logical OR of Two Binary Grids Represented as Quad-Trees](./solutions/0558-logical-or-of-two-binary-grids-represented-as-quad-trees.js)|Medium|
 559|[Maximum Depth of N-ary Tree](./solutions/0559-maximum-depth-of-n-ary-tree.js)|Easy|
 560|[Subarray Sum Equals K](./solutions/0560-subarray-sum-equals-k.js)|Medium|
+561|[Array Partition](./solutions/0561-array-partition.js)|Easy|
 563|[Binary Tree Tilt](./solutions/0563-binary-tree-tilt.js)|Easy|
 564|[Find the Closest Palindrome](./solutions/0564-find-the-closest-palindrome.js)|Hard|
 565|[Array Nesting](./solutions/0565-array-nesting.js)|Medium|

solutions/0561-array-partition.js

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+/**
+ * 561. Array Partition
+ * https://leetcode.com/problems/array-partition/
+ * Difficulty: Easy
+ *
+ * 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.
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var arrayPairSum = function(nums) {
+  return nums.sort((a, b) => a - b).reduce((sum, v, i, a) =>
+    sum + (i % 2 === 0 ? Math.min(v, a[i + 1]) : 0), 0);
+};