二进制取反

class Solution:
    def maxLexicographical(self , num ):
        # write code here
        try:#直接替换100110000的00部分，但是1000会报错
            return num.replace('0','1',num.index('1',num.index('0'))-num.index('0'))
        except:#解决1000的情况
            return num.replace('0','1')

class Solution:
    def maxLexicographical(self , num ):
        # write code here
        res = ''
        for i in range(len(num)):
            if num[i] == '0':
                while i < len(num):
                    if num[i] == '1':
                        res += num[i:]
                        return res
                    res += '1'
                    i += 1
                    if i == len(num):
                        return res
            else:
                res += num[i]
        return res

class Solution:
    def maxLexicographical(self , num ):
        # write code here
        l, r = -1, len(num)-1
        for i in range(len(num)):
            if num[i] == '0' and l==-1:
                l = i
            if num[i] == '1' and l != -1:
                r = i-1
                break
        if l==-1: return num
        res = num[:l] + '1'*len(num[l:r+1]) + num[r+1:]
        return res