【POJ3461】【KMP】Oulipo

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

【分析】

模板

/*
宋代李之仪
卜算子·我住长江头
我住长江头，君住长江尾。日日思君不见君，共饮长江水。 
此水几时休，此恨何时已。只愿君心似我心，定不负相思意。
*/
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
#include <utility>
#include <iomanip>
#include <string>
#include <cmath>
#include <queue>
#include <assert.h>
#include <map>
#include <ctime>
#include <cstdlib>
#include <stack>
#define LOCAL
const int MAXN = 1000000 + 10;
const int INF = 100000000;
const int SIZE = 450;
const int MAXM = 1000000 + 10;
const int maxnode =  0x7fffffff + 10;
using namespace std;
int l1, l2;
char a[MAXN], b[MAXN];
int next[20000];//不用开太大了.. 
void getNext(){
     //初始化next数组 
     next[1] = 0;
     int j = 0;
     for (int i = 2; i <= l1; i++){
         while (j > 0 && a[j + 1] != a[i]) j = next[j];
         if (a[j + 1] == a[i]) j++;
         next[i] = j;
     }
     return;
}
int kmp(){
    int j = 0, cnt = 0;
    for (int i = 1; i <= l2; i++){
        while (j > 0 && a[j + 1] != b[i]) j = next[j];
        if (a[j + 1] == b[i]) j++;
        if (j == l1){
           cnt++;
           j = next[j];//回到上一个匹配点 
        }
    }
    return cnt;
}

void init(){
     scanf("%s", a + 1);
     scanf("%s", b + 1);
     l1 = strlen(a + 1);
     l2 = strlen(b + 1);
}

int main(){
    int T;
    
    scanf("%d", &T);
    while (T--){
          init();
          getNext();
          printf("%d\n", kmp());
    }
    /*scanf("%s", a + 1);
    l1 = strlen(a + 1);
    getNext();
    for (int i = 1; i <= l1; i++) printf("%d ", next[i]);*/
    return 0;
}