Description
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.
Example 1:
Input: s = "01000111" Output: 6 Explanation: The longest balanced substring is "000111", which has length 6.
Example 2:
Input: s = "00111" Output: 4 Explanation: The longest balanced substring is "0011", which has length 4.
Example 3:
Input: s = "111" Output: 0 Explanation: There is no balanced substring except the empty substring, so the answer is 0.
Constraints:
1 <= s.length <= 50'0' <= s[i] <= '1'
Solution
Python3
class Solution:
def findTheLongestBalancedSubstring(self, s: str) -> int:
zeroes = ones = 0
res = 0
for i, x in enumerate(s):
if x == '1':
ones += 1
common = min(zeroes, ones)
res = max(res, common * 2)
else:
if i > 0 and s[i - 1] == '1':
zeroes = 0
zeroes += 1
ones = 0
return res