超级码力初赛第三场 完美字符串

输入: 
s="10101"
k=2
输出: 
2
解释: 
1. 修改 [1,2] ==> "11001"
2. 修改 [2,3] ==> "11111"

输入: 
s="00000"
k=3
输出: 
2
解释:
1. 修改 [0,2] ==> "11100"
2. 修改 [3,4] ==> "11111"

class Solution:
    """
    @param s: string need to be transformed
    @param k: minimum char can be transformed in one operation
    @return: minimum times of transforming all char into '1'
    """
    def perfectString(self, s, k):
        # Write your code here.
        result = 0
        s_len = len(s)
        s_list = list(s)
        for index, s in enumerate(s_list):
            if s == 1:
                continue
            if s == '0':
                start_at = index
                end_at = index
                if end_at+1 <= s_len:
                    while s_list[end_at] == '0' and end_at - start_at < k:
                        end_at = end_at + 1
                        if end_at > s_len -1:
                            break
                    for x in range(start_at, end_at):
                        s_list[x] = '1'

                    result = result + 1
        return result