Add solution #2609

Author: JoshCrozier

README.md

@@ -1940,6 +1940,7 @@
 2601|[Prime Subtraction Operation](./solutions/2601-prime-subtraction-operation.js)|Medium|
 2605|[Form Smallest Number From Two Digit Arrays](./solutions/2605-form-smallest-number-from-two-digit-arrays.js)|Easy|
 2606|[Find the Substring With Maximum Cost](./solutions/2606-find-the-substring-with-maximum-cost.js)|Medium|
+2609|[Find the Longest Balanced Substring of a Binary String](./solutions/2609-find-the-longest-balanced-substring-of-a-binary-string.js)|Easy|
 2615|[Sum of Distances](./solutions/2615-sum-of-distances.js)|Medium|
 2618|[Check if Object Instance of Class](./solutions/2618-check-if-object-instance-of-class.js)|Medium|
 2619|[Array Prototype Last](./solutions/2619-array-prototype-last.js)|Easy|

solutions/2609-find-the-longest-balanced-substring-of-a-binary-string.js

@@ -0,0 +1,45 @@
+/**
+ * 2609. Find the Longest Balanced Substring of a Binary String
+ * https://leetcode.com/problems/find-the-longest-balanced-substring-of-a-binary-string/
+ * Difficulty: Easy
+ *
+ * You are given a binary string s consisting only of zeroes and ones.
+ *
+ * A substring of s is considered balanced if all zeroes are before ones and the number of zeroes
+ * is equal to the number of ones inside the substring. Notice that the empty substring is
+ * considered a balanced substring.
+ *
+ * Return the length of the longest balanced substring of s.
+ *
+ * A substring is a contiguous sequence of characters within a string.
+ */
+
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var findTheLongestBalancedSubstring = function(s) {
+  let result = 0;
+  let zeros = 0;
+  let ones = 0;
+
+  for (let i = 0; i < s.length; i++) {
+    if (s[i] === '0') {
+      if (ones > 0) {
+        zeros = 0;
+        ones = 0;
+      }
+      zeros++;
+    } else {
+      if (zeros >= ones + 1) {
+        ones++;
+        result = Math.max(result, 2 * ones);
+      } else {
+        zeros = 0;
+        ones = 0;
+      }
+    }
+  }
+
+  return result;
+};