---
# System prepended metadata

title: 2609. Find the Longest Balanced Substring of a Binary String
tags: [Leetcode, Easy]

---

# 2609. Find the Longest Balanced Substring of a Binary String
###### tags: `Leetcode` `Easy`
Link: https://leetcode.com/problems/find-the-substring-with-maximum-cost/
## Code
```python=
class Solution:
    def findTheLongestBalancedSubstring(self, s: str) -> int:
        zeroCnt, oneCnt, ans = 0, 0, 0
        for i in range(len(s)):
            if s[i]=='0':
                if oneCnt!=0:
                    zeroCnt, oneCnt = 0, 0
                zeroCnt += 1
            else:
                if oneCnt+1<=zeroCnt:
                    oneCnt += 1
                    ans = max(ans, 2*oneCnt)
        return ans
```