28. Find the Index of the First Occurrence in a String

https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string/

solution

• kmp匹配

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

时间复杂度：O() 空间复杂度：O()