3900. Longest Balanced Substring After One Swap

You are given a binary string s consisting only of characters '0' and '1'. A string is balanced if it contains an equal number of '0's and '1's. You can perform at most one swap between any two characters in s. Then, you select a balanced substring from s. Return an integer representing the maximum length of the balanced substring you can select. Example 1: Input: s = "100001" Output: 4 E