LeetCode每日一题——2609. Find the Longest Balanced Substring of a Binary String

一、题目

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’

二、题解

class Solution {
public:
    int findTheLongestBalancedSubstring(string s) {
        int n = s.length();
        int res = 0;
        for(int i = 0;i < n;i++){
            //过滤到字符串最前面的1
            if(s[i] - '0' == 1) continue;
            int zeroCount = 0;
            int oneCount = 0;
            //统计0的数量
            while(s[i] - '0' == 0 && i < n) zeroCount++,i++;
            //统计1的数量
            while(s[i] - '0' == 1 && i < n) oneCount++,i++;
            i--;
            res = max(res,min(zeroCount,oneCount) * 2);
        }
        return res;
    }
};
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