HDU 1686 (KMP)

Oulipo

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 9731    Accepted Submission(s): 3859

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
   
   
   
   

 

题意：求文本串里面有多少个模式串。

KMP中每次j遍历到m-1时表示一次匹配成功，下一次匹配肯定是从当前的i和next[j]开始

的，然后继续匹配就可以了。

不知道为什么hash过不去~

#include <cstring>
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <cmath>
using namespace std;
#define maxn 1111111

char P[maxn], T[maxn];
int n, m;
#define next Next
int next[maxn];

void get_next (char *p) {  
    int t;  
    t = next[0] = -1;  
    int j = 0;  
    while (j+1 < m) {  
        if (t < 0 || p[j] == p[t]) {//匹配  
            j++, t++;  
            next[j] = t;
        }  
        else //失配  
            t = next[t];  
    }  
}  

int kmp () {
	int ans = 0;
	get_next (P);
	int i = 0, j = 0;
	while (i < n && j < m) { 
		if (j < 0 || T[i] == P[j]) {
			if (j == m-1) {
				ans++;
				j = next[j];
				continue;
			}
			i++, j++;
		}
		else {
			j = next[j];
		}
	}
	return ans;
}

int main () {
	int cas;
	cin >> cas;
	while (cas--) {
		scanf ("%s%s", P, T);
		n = strlen (T);
		m = strlen (P);
		printf ("%d\n", kmp ());
	}
	return 0;
}