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Period(kmp)

时间:2015-08-07 21:53:10      阅读:109      评论:0      收藏:0      [点我收藏+]

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Period

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 4437    Accepted Submission(s): 2145


Problem Description
For each prefix of a given string S with N characters (each character has an ASCII code between 97 and 126, inclusive), we want to know whether the prefix is a periodic string. That is, for each i (2 <= i <= N) we want to know the largest K > 1 (if there is one) such that the prefix of S with length i can be written as AK , that is A concatenated K times, for some string A. Of course, we also want to know the period K.
 

 

Input
The input file consists of several test cases. Each test case consists of two lines. The first one contains N (2 <= N <= 1 000 000) – the size of the string S. The second line contains the string S. The input file ends with a line, having the number zero on it.
 

 

Output
For each test case, output “Test case #” and the consecutive test case number on a single line; then, for each prefix with length i that has a period K > 1, output the prefix size i and the period K separated by a single space; the prefix sizes must be in increasing order. Print a blank line after each test case.
 

 

Sample Input
3 aaa 12 aabaabaabaab 0
 

 

Sample Output
Test case #1 2 2 3 3 Test case #2 2 2 6 2 9 3 12 4
 题解看了半天题意,,题意:给定一个字符串,问这个字符串的所有前缀中,有哪些前缀可以由某个串重复k次组成,
    并且这个k最大是多少。这个k需要大于1。于是我们可以想到,next【i】的值就是长度,当i%next[i]==0是开始匹配i/next[i]便是重复度k;
代码贴上:
 1 #include<stdio.h>
 2 const int MAXN=1000010;
 3 int N;
 4 char m[MAXN];
 5 int next[MAXN];
 6 void getnext(){
 7     int i=0,j=-1;
 8     next[i]=j;
 9     while(i<N){
10         if(j==-1||m[i]==m[j]){
11             i++;j++;
12             next[i]=j;
13         }
14         else j=next[j];
15     }
16 }
17 void print(int x){
18      for(int i=1;i<=x;i++){
19          if(next[i]!=0&&i%(i-next[i])==0)printf("%d %d\n",i,i/(i-next[i]));
20      }
21 }
22 int main(){
23     int flot=0;
24     while(~scanf("%d",&N),N){
25         scanf("%s",m);
26         getnext();
27         //for(int i=0;i<=N;i++)printf("%d ",next[i]);puts("");
28         //if(flot)puts("");
29         printf("Test case #%d\n",++flot);
30         print(N);
31         puts("");
32     }
33     return 0;
34 }

 

 

Period(kmp)

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原文地址:http://www.cnblogs.com/handsomecui/p/4711719.html

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