正题

ybtoj KMP-2

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题目大意

问你一个字符串最多由多少个相同的字符串组合而成

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解题思路

如下图，先用KMP求出nx数组，那么有$1\sim n{x}_n$和$(n-n{x}_n)\sim n$相匹配

不难推出$1\sim (n-n{x}_n)$和$n{x}_n\sim n$匹配，则$n{x}_n\sim n$为最小的相同的字符串

如果$(n-n{x}_n)\mid n$那么有解

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代码

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define ll long long
#define N 1000100
using namespace std;
int nx[N];
char str[N];
void gnx(char* s) {int n = strlen(s + 1);for (int i = 2, j = 0; i <= n; ++i) {while (s[i] != s[j + 1] && j) j = nx[j];if (s[i] == s[j + 1])j++;nx[i] = j;}return;
}
int main() {scanf("%s", str + 1);while (str[1] != '.') {gnx(str);int n = strlen(str + 1);nx[1] = 0;if (n % (n - nx[n]) == 0)//判断是否有解printf("%d\n", n / (n - nx[n]));elseputs("1");scanf("%s", str + 1);}return 0;
}