Add solution #1224

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,186 LeetCode solutions in JavaScript
+# 1,187 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -940,6 +940,7 @@
 1220|[Count Vowels Permutation](./solutions/1220-count-vowels-permutation.js)|Hard|
 1222|[Queens That Can Attack the King](./solutions/1222-queens-that-can-attack-the-king.js)|Medium|
 1223|[Dice Roll Simulation](./solutions/1223-dice-roll-simulation.js)|Hard|
+1224|[Maximum Equal Frequency](./solutions/1224-maximum-equal-frequency.js)|Hard|
 1232|[Check If It Is a Straight Line](./solutions/1232-check-if-it-is-a-straight-line.js)|Easy|
 1233|[Remove Sub-Folders from the Filesystem](./solutions/1233-remove-sub-folders-from-the-filesystem.js)|Medium|
 1249|[Minimum Remove to Make Valid Parentheses](./solutions/1249-minimum-remove-to-make-valid-parentheses.js)|Medium|

solutions/1224-maximum-equal-frequency.js

@@ -0,0 +1,47 @@
+/**
+ * 1224. Maximum Equal Frequency
+ * https://leetcode.com/problems/maximum-equal-frequency/
+ * Difficulty: Hard
+ *
+ * Given an array nums of positive integers, return the longest possible length of an array prefix
+ * of nums, such that it is possible to remove exactly one element from this prefix so that every
+ * number that has appeared in it will have the same number of occurrences.
+ *
+ * If after removing one element there are no remaining elements, it's still considered that every
+ * appeared number has the same number of ocurrences (0).
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var maxEqualFreq = function(nums) {
+  const countMap = new Map();
+  const freqMap = new Map();
+  let result = 0;
+
+  for (let i = 0; i < nums.length; i++) {
+    const num = nums[i];
+    const prevCount = countMap.get(num) || 0;
+    const newCount = prevCount + 1;
+
+    countMap.set(num, newCount);
+
+    if (prevCount > 0) {
+      freqMap.set(prevCount, (freqMap.get(prevCount) || 0) - 1);
+      if (freqMap.get(prevCount) === 0) freqMap.delete(prevCount);
+    }
+    freqMap.set(newCount, (freqMap.get(newCount) || 0) + 1);
+
+    if (freqMap.size === 1) {
+      const [freq, occurrences] = [...freqMap.entries()][0];
+      if (freq === 1 || occurrences === 1) result = i + 1;
+    } else if (freqMap.size === 2) {
+      const freqs = [...freqMap.keys()].sort((a, b) => a - b);
+      if (freqs[0] === 1 && freqMap.get(freqs[0]) === 1) result = i + 1;
+      if (freqs[1] === freqs[0] + 1 && freqMap.get(freqs[1]) === 1) result = i + 1;
+    }
+  }
+
+  return result;
+};