hdu Oulipo(kmp)

Problem Description

The French author Georges Perec (1936–1982) once wrote a book, La disparition, without the letter 'e'. He was a member of the Oulipo group. A quote from the book:

Tout avait Pair normal, mais tout s’affirmait faux. Tout avait Fair normal, d’abord, puis surgissait l’inhumain, l’affolant. Il aurait voulu savoir où s’articulait l’association qui l’unissait au roman : stir son tapis, assaillant à tout instant son imagination, l’intuition d’un tabou, la vision d’un mal obscur, d’un quoi vacant, d’un non-dit : la vision, l’avision d’un oubli commandant tout, où s’abolissait la raison : tout avait l’air normal mais…

Perec would probably have scored high (or rather, low) in the following contest. People are asked to write a perhaps even meaningful text on some subject with as few occurrences of a given “word” as possible. Our task is to provide the jury with a program that counts these occurrences, in order to obtain a ranking of the competitors. These competitors often write very long texts with nonsense meaning; a sequence of 500,000 consecutive 'T's is not unusual. And they never use spaces.

So we want to quickly find out how often a word, i.e., a given string, occurs in a text. More formally: given the alphabet {'A', 'B', 'C', …, 'Z'} and two finite strings over that alphabet, a word W and a text T, count the number of occurrences of W in T. All the consecutive characters of W must exactly match consecutive characters of T. Occurrences may overlap.

 

Input

The first line of the input file contains a single number: the number of test cases to follow. Each test case has the following format:

One line with the word W, a string over {'A', 'B', 'C', …, 'Z'}, with 1 ≤ |W| ≤ 10,000 (here |W| denotes the length of the string W).
One line with the text T, a string over {'A', 'B', 'C', …, 'Z'}, with |W| ≤ |T| ≤ 1,000,000.

 

Output

For every test case in the input file, the output should contain a single number, on a single line: the number of occurrences of the word W in the text T.

 

Sample Input

3

BAPC

BAPC

AZA

AZAZAZA

VERDI

AVERDXIVYERDIAN

 

Sample Output

1
3
0

 

Source

华东区大学生程序设计邀请赛_热身赛

 

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代码:

 #include <vector>
 #include <map>
 #include <set>
 #include <algorithm>
 #include <iostream>
 #include <cstdio>
 #include <cmath>
 #include <cstdlib>
 #include <string>
 #include <cstring>
 #include <queue>
 using namespace std;
 #define INF 0x3f3f3f3f

 char p[],s[];
 int nex[];

 void get(char *p)
 {
     int plen=strlen(p);
     nex[]=-;
     int k=-,j=;
     while(j < plen){
         if(k==- || p[j] == p[k]){
             ++j;
             ++k;
             if(p[j] != p[k])
                 nex[j]=k;
             else
                 nex[j]=nex[k];
         }
         else{
             k=nex[k];
         }
     }
 }

 int kmp(char *s,char *p)
 {
     int i=,j=,ans=;
     int slen=strlen(s);
     int plen=strlen(p);
     while(i < slen && j< plen){
         if(j==- || s[i]==p[j]){
             ++i;
             ++j;
         }
         else{
             j=nex[j];
         }
         if(j == plen){  //重点注意，这里是为了回到当匹配完后，next[j]应该回到的位置
             j=nex[j];   //例： a="aza" b="azazaza" 第一次结束后，next[j]应该所指的位置为a中的‘z’,然后继续匹配
             ans++;
         }
     }

     return ans;
 }

 int main()
 {
     int t;
     scanf("%d",&t);
     while(t--){
         scanf("%s",p);
         scanf("%s",s);
         get(p);
         printf("%d\n",kmp(s,p));
     }
 }