2015
02-22

# Cyclic Nacklace

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.

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 ).

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 ).

3
aaa
abca
abcde

0
2
5

http://acm.hdu.edu.cn/showproblem.php?pid=3746

kmp的Nxet数组求字符串循环节例题

lenB%(lenB-Next[lenB])==0则其有周期lenB/(lenB-Next[lenB])，其中最小循环节长度是lenB-Next[lenB]

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std ;
char B[100005] ;
int Next[100005],lenB ;
void GetNext()
{
int i,j ;
Next[1]=0 ;
j=0 ;
for(i=2 ;i<=lenB ;i++)
{
while(j>0 && (B[j+1]!=B[i]))j=Next[j] ;
if(B[j+1]==B[i])j++ ;
Next[i]=j ;
}
}
int main()
{
int t ;
scanf("%d",&t) ;
while(t--)
{
scanf("%s",B+1) ;
lenB=strlen(B+1) ;
GetNext() ;
int minn=lenB-Next[lenB] ;
if(!Next[lenB])printf("%d\n",lenB) ;
else if(lenB%minn)
printf("%d\n",minn-lenB%minn) ;
else
printf("0\n") ;
}
return 0 ;
}

1. 代码是给出了，但是解析的也太不清晰了吧！如 13 abejkcfghid jkebfghicda
第一步拆分为 三部分 (bejk, cfghi, d) * C(13,3)，为什么要这样拆分，原则是什么？

2. 你的理解应该是：即使主持人拿走一个箱子对结果没有影响。这样想，主持人拿走的箱子只是没有影响到你初始选择的那个箱子中有奖品的概率，但是改变了其余两个箱子的概率分布。由 1/3,1/3 变成了 0, 2/3