leetcode 28 str()

使用朴素匹配方法。

class Solution:
    def strStr(self, haystack: str, needle: str) -> int:
        if haystack=="" and needle!="":
            return -1
        if needle=="":
            return 0
        haystack=list(haystack)
        flag=True
        i=0
        while i+len(needle)<=len(haystack):
            if haystack[i]==needle[0]:
                flag=True
                for j in range(1,len(needle)):

                    if needle[j]!=haystack[i+j]:

                        flag=False
                        break                 

                if flag:
                    return i
            i+=1

        return -1