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2723. Find the Longest Balanced Substring of a Binary String

My accepted Python solution to LeetCode problem 2723, Find the Longest Balanced Substring of a Binary String, running in 0ms.

  • Difficulty: Easy
  • Python
  • Runtime 0ms
  • Memory 17.3MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

Python

Accepted on LeetCode — runtime 0ms, memory 17.3MB, accepted 2026-01-01.

python
class Solution:
    def findTheLongestBalancedSubstring(self, s: str) -> int:
        max_len = 0
        zeros = 0
        ones = 0
        
        for c in s:
            if c == '0':
                if ones > 0:  # Reset when we see 0 after seeing 1
                    zeros = 0
                    ones = 0
                zeros += 1
            else:  # c == '1'
                ones += 1
                # Update max length: balanced means min(zeros, ones) pairs
                max_len = max(max_len, 2 * min(zeros, ones))
        
        return max_len

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