POJ 3461 Oulipo KMP

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

题目大意是这样的：
跟你多组数据， 每组数据中包含两个字符串W和T，询问W在T中出现了多少次。

显然要用KMP

#include <iostream>#include <cstdio>#include <cstring>using namespace  std;const int SZ = 10010;const int LA = 1000010;int nxt[SZ];void getnxt(char n[]){    nxt[0] = nxt[1] = 0;    int len = strlen(n);    for(int i = 1; i < len; i ++)    {        int j = nxt[i];        while(j && n[i] != n[j])    j = nxt[j];        nxt[i + 1] = (n[i] == n[j] ? j + 1 : 0);    }}int kmp(char n[], char m[]){    int ans = 0;    int len1 = strlen(n), len2 = strlen(m);    for(int i = 0, j = 0; i < len2; i ++)    {        while(j && n[j] != m[i]) j = nxt[j];        if(n[j] == m[i]) j ++;        if(j == len1)   ans ++;    }    return ans;}int main(){    int t;    scanf("%d", &t);    while(t --)    {        memset(nxt, 0, sizeof(nxt));        char n[SZ], m[LA];        scanf("%s", n);        scanf("%s", m);        getnxt(n);        printf("%d\n", kmp(n, m));    }}