POJ_2752_KMP

http://poj.org/problem?id=2752

求字符串的字串，使前缀后缀都为这个字串，按字母数量排序输出数量。

用了KMP的未优化的next数组。

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

char a[400005];
int ans[400005],next[400005];

void get_next(int len)
{
    int i = 0,j = -1;
    next[0] = -1;
    while(i < len)
    {
        if(j == -1 || a[i] == a[j])
        {
            ++i;
            ++j;
            next[i] = j;
        }
        else    j = next[j];
    }
}
int main()
{
    while(~scanf("%s",a))
    {
        int cnt = 0,len = strlen(a);
        int now = len;
        get_next(len);
        while(now != 0)
        {
            now = next[now];
            ans[cnt++] = now;
        }
        for(int i = cnt-2;i >= 0;i--)   printf("%d ",ans[i]);
        printf("%d
",len);
    }
    return 0;
}