Leetcode 1702. Maximum Binary String After Change

class Solution:
    def maximumBinaryString(self, binary: str) -> str:
        digits = list(binary)
        n = len(digits)
        i = 0
        while i < n and digits[i] != '0':
            i += 1
        m = i
        while i < n and digits[i] != '1':
            i += 1
        k = i
        for j in range(i, n):
            if digits[j] == '0':
                digits[j] = '1'
                digits[k] = '0'
                k += 1
        i = m
        while i < n - 1 and digits[i] == '0' and digits[i+1] == '0':
            digits[i] = '1'
            i += 1
        ans = ''.join(digits)
        return ans

class Solution:
    def maximumBinaryString(self, binary: str) -> str:
        digits = list(binary)
        n = len(digits)
        i = 0
        while i < n and digits[i] != '0':
            i += 1
        digits = digits[:i] + sorted(digits[i:])
        i = 0 
        while i < n - 1:
            if digits[i] == '0' and digits[i+1] == '0':
                digits[i] = '1'
            i += 1

        ans = ''.join(digits)
        return ans

class Solution:
    def maximumBinaryString(self, binary: str) -> str:
        digits = ['1'] * len(binary)
        count = binary.count('0')
        if count <= 1:
            return binary
        n = len(digits)
        i = 0
        while i < n and binary[i] != '0':
            i += 1
        digits[i+count-1] = '0'
        ans = ''.join(digits)
        return ans