poj1961 (kmp algorithm next array of applications)

Topic link: https: //vjudge.net/problem/POJ-1961

The meaning of problems: Given a string of length n, (n <= 1e6), for index i (2 <= i <= n), if the substring s (1 ... i) is a periodic sub-string output The maximum period.

Ideas:

　　Investigation of the algorithm defined kmp next master array, if the (i + 1)% (ij) == 0 && (i + 1) / (ij)> 1, then the condition is met when the substring.

AC Code:

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;

const int maxn=1e6+5;
int n,cas,nex[maxn];
char s[maxn];

void get_next(){
    int j;
    j=nex[0]=-1;
    for(int i=1;i<n;++i){
        while(j>-1&&s[i]!=s[j+1]) j=nex[j];
        if(s[i]==s[j+1]) ++j;
        nex[i]=j;
        if((i+1)%(i-j)==0&&(i+1)/(i-j)>1)
            printf("%d %d\n",i+1,(i+1)/(i-j));
    }
}

int main(){
    while(scanf("%d",&n),n){
        scanf("%s",s);
        printf("Test case #%d\n",++cas);
        get_next();
        printf("\n");
    }
    return 0;
}