LeetCode 459. Repeated Substring Pattern KMP-优快云博客

本文链接：https://blog.youkuaiyun.com/taoqick/article/details/107443036

本文介绍了一种算法，用于检查一个非空字符串是否可以通过其子串的多次复制来构造。通过两个解决方案，KMP算法和字符串查找，展示了如何判断字符串是否符合特定的重复模式。

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Given a non-empty string check if it can be constructed by taking a substring of it and appending multiple copies of the substring together. You may assume the given string consists of lowercase English letters only and its length will not exceed 10000.

Example 1:

Input: "abab"
Output: True
Explanation: It's the substring "ab" twice.

Example 2:

Input: "aba"
Output: False

Example 3:

Input: "abcabcabcabc"
Output: True
Explanation: It's the substring "abc" four times. (And the substring "abcabc" twice.)

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Solution 1:KMP

The meaning of nxt arr is https://blog.youkuaiyun.com/taoqick/article/details/12979371

class Solution:
    def repeatedSubstringPattern(self, s: str) -> bool:
        l = len(s)
        nxt = [-1 for i in range(l+1)]
        i,j = 0,-1
        while (i < l):
            if (j == -1 or s[i] == s[j]):
                i,j = i+1,j+1
                nxt[i] = j
            else:
                j = nxt[j]
        #print(nxt)
        return nxt[l] > 0 and l % (l-nxt[l]) == 0

s = Solution()
print(s.repeatedSubstringPattern("abcabcabc"))

Solution 2: str find:

class Solution:
    def repeatedSubstringPattern(self, s: str) -> bool:
        ss = s + s
        return s in ss[1:-1]

s = Solution()
print(s.repeatedSubstringPattern("abcabcabc"))