hdu 1358 Period

kmp算法的应用。

kmp算法入门http://billhoo.blog.51cto.com/2337751/411486

字符串偏移量为i-next[i]，i为字符串的当前前缀长度。若偏移量能够被前缀长度整除，则该前缀可写为A^B。

#include <iostream>#include <cstdio>#include <cstring>using namespace std;void getNext(char *str,int *next){int len = strlen(str);int j = 0;next[1] = 0;for(int i = 2;i<len+1;i++){while(j>0&&str[j]!=str[i-1]){j = next[j];}if(str[j]==str[i-1])j++;next[i] = j;}}char str[1000005];int next[1000005];int main(){int n,k=1;while(scanf("%d",&n)&&n){scanf("%s",str);getNext(str,next);printf("Test case #%d\n",k++);for(int i = 1;i<=n;i++){int tmp = i-next[i];if(tmp&&i%tmp==0){if(i/tmp>1)printf("%d %d\n",i,i/tmp);}}printf("\n");}return 0;}