UVaLA 3026 Period MP算法

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MP算法求失配函数

对于f [] 数组的定义如下：

 

　1) f[j] = 0  j = 0,1

 

　2) f[j] = max(k): 0<k<j   P[0...k-1]=P[j-k,j-1]

 

#include <cstdio>#include <cstring>#include <iostream>using namespace std;const int MAXN = 1000000 + 10;char P[MAXN];int n, f[MAXN];//失配函数求 f 数组void getFail(){    f[0] = f[1] = 0;        //递推边界初值    for (int i = 1; i <= n; i++)    {        int j = f[i];        while (j && P[i] != P[j]) j = f[j];        f[i + 1] = P[i] == P[j] ? j + 1 : 0;    }}int main(){    int kase = 0;    while (~scanf("%d", &n) && n)    {        scanf("%s", P);        getFail();        printf("Test case #%d\n", ++kase);        for (int i = 2; i <= n; i++)            if (f[i] > 0 && i % (i - f[i]) == 0)                printf("%d %d\n", i, i / (i - f[i]));        printf("\n");    }    return 0;}