POJ2752Seek the Name, Seek the Fame

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn=400010;
char b[maxn];
int next[maxn],a[maxn];
void prekmp()
{
    int j=-1;next[0]=-1;
    for(int i=1;b[i];++i)
    {
        while(j!=-1&&b[i]!=b[j+1]) j=next[j];
        if(b[i]==b[j+1]) j++;
        next[i]=j;
    }
}
int main()
{
    while(scanf("%s",b)!=EOF)
    {
        prekmp();
        int len=strlen(b);
        int i=-1;
        for(int j=len-1;j!=-1;j=next[j])
        {
            a[++i]=j+1;
        }
        for(;i>0;--i) printf("%d ",a[i]);
        printf("%d\n",a[0]);
    }
    return 0;
}