add 2609

Author: fishercoder1534

Diff for: paginated_contents/algorithms/3rd_thousand/README.md

@@ -22,6 +22,7 @@
 | 2643 | [Row With Maximum Ones](https://leetcode.com/problems/row-with-maximum-ones/)                                                                                       | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2643.java)                                       |                                      | Easy                           |
 | 2641 | [Cousins in Binary Tree II](https://leetcode.com/problems/cousins-in-binary-tree-ii/)                                                                                       | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2641.java)                                       |                                      | Medium                         |Tree, BFS, HashTable
 | 2605 | [Form Smallest Number From Two Digit Arrays](https://leetcode.com/problems/form-smallest-number-from-two-digit-arrays/)                                                                                       | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2605.java)                                       |                                      | Easy                           |
+| 2609 | [Find the Longest Balanced Substring of a Binary String](https://leetcode.com/problems/find-the-longest-balanced-substring-of-a-binary-string/)                                                                                       | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2609.java)                                       |                                      | Easy                           |
 | 2600 | [K Items With the Maximum Sum](https://leetcode.com/problems/k-items-with-the-maximum-sum/)                                                                                       | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2600.java)                                       |                                      | Easy                           |
 | 2596 | [Check Knight Tour Configuration](https://leetcode.com/problems/check-knight-tour-configuration/)                                                                                            | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2596.java)                                       | [:tv:](https://youtu.be/OBht8NT_09c) | Medium                         |
 | 2595 | [Number of Even and Odd Bits](https://leetcode.com/problems/number-of-even-and-odd-bits/)                                                                                                    | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2595.java)                                       |                                      | Easy                           |

Diff for: src/main/java/com/fishercoder/solutions/thirdthousand/_2609.java

@@ -0,0 +1,28 @@
+package com.fishercoder.solutions.thirdthousand;
+
+public class _2609 {
+    public static class Solution1 {
+        public int findTheLongestBalancedSubstring(String s) {
+            int longest = 0;
+            for (int i = 0; i < s.length(); i++) {
+                if (s.charAt(i) == '0') {
+                    int zeroes = 0;
+                    while (i < s.length() && s.charAt(i) == '0') {
+                        i++;
+                        zeroes++;
+                    }
+                    if (i < s.length()) {
+                        int ones = 0;
+                        while (i < s.length() && s.charAt(i) == '1') {
+                            i++;
+                            ones++;
+                        }
+                        longest = Math.max(longest, Math.min(ones, zeroes) * 2);
+                        i--;
+                    }
+                }
+            }
+            return longest;
+        }
+    }
+}

Diff for: src/test/java/com/fishercoder/thirdthousand/_2609Test.java

@@ -0,0 +1,27 @@
+package com.fishercoder.thirdthousand;
+
+import com.fishercoder.solutions.thirdthousand._2609;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class _2609Test {
+    private static _2609.Solution1 solution1;
+
+    @BeforeEach
+    public void setup() {
+        solution1 = new _2609.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals(6, solution1.findTheLongestBalancedSubstring("01000111"));
+    }
+
+    @Test
+    public void test2() {
+        assertEquals(2, solution1.findTheLongestBalancedSubstring("001"));
+    }
+
+}