hdu 3746 KMP 循环节

Cyclic Nacklace

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 9671    Accepted Submission(s): 4131

Problem Description

CC always becomes very depressed at the end of this month, he has checked his credit card yesterday, without any surprise, there are only 99.9 yuan left. he is too distressed and thinking about how to tide over the last days. Being inspired by the entrepreneurial spirit of "HDU CakeMan", he wants to sell some little things to make money. Of course, this is not an easy task.

As Christmas is around the corner, Boys are busy in choosing christmas presents to send to their girlfriends. It is believed that chain bracelet is a good choice. However, Things are not always so simple, as is known to everyone, girl's fond of the colorful decoration to make bracelet appears vivid and lively, meanwhile they want to display their mature side as college students. after CC understands the girls demands, he intends to sell the chain bracelet called CharmBracelet. The CharmBracelet is made up with colorful pearls to show girls' lively, and the most important thing is that it must be connected by a cyclic chain which means the color of pearls are cyclic connected from the left to right. And the cyclic count must be more than one. If you connect the leftmost pearl and the rightmost pearl of such chain, you can make a CharmBracelet. Just like the pictrue below, this CharmBracelet's cycle is 9 and its cyclic count is 2:

Now CC has brought in some ordinary bracelet chains, he wants to buy minimum number of pearls to make CharmBracelets so that he can save more money. but when remaking the bracelet, he can only add color pearls to the left end and right end of the chain, that is to say, adding to the middle is forbidden.
CC is satisfied with his ideas and ask you for help.

 

Input

The first line of the input is a single integer T ( 0 < T <= 100 ) which means the number of test cases.
Each test case contains only one line describe the original ordinary chain to be remade. Each character in the string stands for one pearl and there are 26 kinds of pearls being described by 'a' ~'z' characters. The length of the string Len: ( 3 <= Len <= 100000 ).

 

Output

For each case, you are required to output the minimum count of pearls added to make a CharmBracelet.

 

Sample Input

3 aaa abca abcde

 

Sample Output

0 2 5

 

题意：在字符串末尾添加几个字符可以使原字符串至少拥有两个循环节。

 

这是道KMP，不过考了对next数组的灵活运用。

由于题目要求在原字符串右边添加字符，所以直接看最后一个字符的next值，最后一个字符的next值可以分两种情况：

第一种，next等于0,说明在此之前不存在任何循环节，所以要在后面加上整个原字符串才能有两个循环节。

第二种，next大于0，思考一下，我们就会知道，因为next[len]表示字符串最长公共前后缀长度，所以len-next[len]为循环节长度，所以我们就知道该在最后加多少个字符构成循环节了。

 

#include<iostream>
#include<string>
#include<string.h>
#include<stdio.h>
#define MAX_N 100005

using namespace std;

char s[MAX_N];
int nexxt[MAX_N];
int len;
void getNext()
{
    nexxt[0]=-1;
    int i = 0,j = -1;
    len=strlen(s);
    while(i<=len)
    {
        if(j==-1 || s[i]==s[j])
        {
            i++,j++;
            nexxt[i]=j;
        }
        else
            j=nexxt[j];
    }
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%s",s);
        getNext();
        int cir = len-nexxt[len];
        if(len%cir==0 && cir!=len)
            cout<<0<<endl;
        else
            cout<<cir-nexxt[len]%cir<<endl;
    }
    return 0;
}