28. Implement strStr()

problem

Implement strStr().

Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

求第二个字符串在第一个字符串中的位置
注意，字符串不定长

solution

range(-100) = []

import bisect
class Solution(object):
    def strStr(self, haystack, needle):
        """
        :type haystack: str
        :type needle: str
        :rtype: int
        """
        step = len(needle)
        for j in range(len(haystack)-len(needle)+1):
            if haystack[j:j+step] == needle:
                return j
        return -1