Add solution #1664

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,459 LeetCode solutions in JavaScript
+# 1,460 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1282,6 +1282,7 @@
 1659|[Maximize Grid Happiness](./solutions/1659-maximize-grid-happiness.js)|Hard|
 1662|[Check If Two String Arrays are Equivalent](./solutions/1662-check-if-two-string-arrays-are-equivalent.js)|Easy|
 1663|[Smallest String With A Given Numeric Value](./solutions/1663-smallest-string-with-a-given-numeric-value.js)|Medium|
+1664|[Ways to Make a Fair Array](./solutions/1664-ways-to-make-a-fair-array.js)|Medium|
 1668|[Maximum Repeating Substring](./solutions/1668-maximum-repeating-substring.js)|Easy|
 1669|[Merge In Between Linked Lists](./solutions/1669-merge-in-between-linked-lists.js)|Medium|
 1672|[Richest Customer Wealth](./solutions/1672-richest-customer-wealth.js)|Easy|

solutions/1664-ways-to-make-a-fair-array.js

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+/**
+ * 1664. Ways to Make a Fair Array
+ * https://leetcode.com/problems/ways-to-make-a-fair-array/
+ * Difficulty: Medium
+ *
+ * You are given an integer array nums. You can choose exactly one index (0-indexed) and remove
+ * the element. Notice that the index of the elements may change after the removal.
+ *
+ * For example, if nums = [6,1,7,4,1]:
+ * - Choosing to remove index 1 results in nums = [6,7,4,1].
+ * - Choosing to remove index 2 results in nums = [6,1,4,1].
+ * - Choosing to remove index 4 results in nums = [6,1,7,4].
+ *
+ * An array is fair if the sum of the odd-indexed values equals the sum of the even-indexed values.
+ *
+ * Return the number of indices that you could choose such that after the removal, nums is fair.
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var waysToMakeFair = function(nums) {
+  let evenSum = 0;
+  let oddSum = 0;
+  let result = 0;
+
+  for (let i = 0; i < nums.length; i++) {
+    if (i % 2 === 0) evenSum += nums[i];
+    else oddSum += nums[i];
+  }
+
+  let currentEven = 0;
+  let currentOdd = 0;
+
+  for (let i = 0; i < nums.length; i++) {
+    if (i % 2 === 0) {
+      evenSum -= nums[i];
+      if (currentEven + oddSum === currentOdd + evenSum) result++;
+      currentEven += nums[i];
+    } else {
+      oddSum -= nums[i];
+      if (currentEven + oddSum === currentOdd + evenSum) result++;
+      currentOdd += nums[i];
+    }
+  }
+
+  return result;
+};