POJ 3461 Oulipo 【KMP统计子串数】

传送门：http://poj.org/problem?id=3461

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 50450		Accepted: 20018

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

BAPC 2006 Qualification

KMP模板：

 #include <cstdio>
 #include <iostream>
 #include <cstring>
 #include <algorithm>
 #define INF 0x3f3f3f3f
 #define LL long long
 using namespace std;
 const int MAXN = 1e6+;
 const int MAXW = 1e4+;
 char W[MAXW], T[MAXN];
 int wlen, tlen;
 int nxt[MAXW];

 void get_Next()
 {
     int j = , k = -;
     nxt[] = -;
     while(j < wlen){
         if(k == - || W[j] == W[k]){
             nxt[++j] = ++k;
         }
         else k = nxt[k];
     }
 }

 int KMP_count()
 {
     int ans = , j = ;
     if(wlen ==  && tlen == ){
         if(W[] == T[]) return ;
         else return ;
     }
     get_Next();
     for(int now = ; now < tlen; now++){
         while(j >  && T[now] != W[j])
             j = nxt[j];
         if(W[j] == T[now]) j++;
         if(j == wlen){
             ans++;
             j = nxt[j];
         }
     }
     return ans;
 }

 int main()
 {
     int T_case;
     scanf("%d", &T_case);
     while(T_case--){
         scanf("%s%s", &W, &T);
         wlen = strlen(W);
         tlen = strlen(T);

         printf("%d\n", KMP_count());
     }
     return ;
 }