代码随想录算法训练营第九天| 28.找出字符串中第一个匹配项的下标 459.重复的子字符串

28.找出字符串中第一个匹配项的下标

题目链接： https://leetcode.cn/problems/find-the-index-of-the-first-occurrence-in-a-string/

思路：暴力了

class Solution:
    def strStr(self, haystack: str, needle: str) -> int:
        x = len(haystack)
        y = len(needle)


        if x == 0 or y > x:
            return -1
        if y == 0:
            return 0
        
        for i in range(x-y+1):
            if haystack[i] == needle[0]:
                if haystack[i:i+y] == needle:
                    return i

        return -1

459.重复的子字符串

题目链接： https://leetcode.cn/problems/repeated-substring-pattern/

实话 KMP我还得研究 不是特别懂

def go_next(nxt, s):
    nxt[0] = -1
    j = -1
    for i in range(1,len(s)):
        while j >= 0 and s[i] != s[j+1]:
            j = nxt[j]
        if s[i] == s[j+1]:
            j += 1
        nxt[i] = j
    return nxt

class Solution:
    def repeatedSubstringPattern(self, s: str) -> bool:
        if len(s) == 0:
            return False
        nxt = [0] * len(s)
        go_next(nxt, s)
        if nxt[-1] != -1 and len(s)%(len(s)-(nxt[-1]+1)) == 0:
            return True
        return False