Add solution #1399

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,280 LeetCode solutions in JavaScript
+# 1,281 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1067,6 +1067,7 @@
 1395|[Count Number of Teams](./solutions/1395-count-number-of-teams.js)|Medium|
 1396|[Design Underground System](./solutions/1396-design-underground-system.js)|Medium|
 1397|[Find All Good Strings](./solutions/1397-find-all-good-strings.js)|Hard|
+1399|[Count Largest Group](./solutions/1399-count-largest-group.js)|Easy|
 1400|[Construct K Palindrome Strings](./solutions/1400-construct-k-palindrome-strings.js)|Medium|
 1402|[Reducing Dishes](./solutions/1402-reducing-dishes.js)|Hard|
 1408|[String Matching in an Array](./solutions/1408-string-matching-in-an-array.js)|Easy|

solutions/1399-count-largest-group.js

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+/**
+ * 1399. Count Largest Group
+ * https://leetcode.com/problems/count-largest-group/
+ * Difficulty: Easy
+ *
+ * You are given an integer n.
+ *
+ * Each number from 1 to n is grouped according to the sum of its digits.
+ *
+ * Return the number of groups that have the largest size.
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var countLargestGroup = function(n) {
+  const map = new Map();
+  let maxSize = 0;
+
+  for (let num = 1; num <= n; num++) {
+    const digitSum = calculateDigitSum(num);
+    const size = (map.get(digitSum) || 0) + 1;
+    map.set(digitSum, size);
+    maxSize = Math.max(maxSize, size);
+  }
+
+  let result = 0;
+  for (const size of map.values()) {
+    if (size === maxSize) result++;
+  }
+
+  return result;
+};
+
+function calculateDigitSum(num) {
+  let sum = 0;
+  while (num > 0) {
+    sum += num % 10;
+    num = Math.floor(num / 10);
+  }
+  return sum;
+}