1316：不同的循环子字符串（1836 分）

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class Solution:
    def distinctEchoSubstrings(self, text: str) -> int:
        n = len(text)
        f = [[0]*(n+1) for _ in range(n)]
        res = set()
        for i in range(n-2,-1,-1):
            for j in range(i+1,n):
                f[i][j] = 0 if text[i]!=text[j] else 1+f[i+1][j+1] 
                if f[i][j]>=j-i:
                    res.add(text[i:j])
        return len(res)