hdu 1686 Oulipo (KMP)

Oulipo
Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 22615    Accepted Submission(s): 8746

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

C/C++：

#include <map>
#include <queue>
#include <cmath>
#include <vector>
#include <string>
#include <cstdio>
#include <cstring>
#include <climits>
#include <iostream>
#include <algorithm>
#define INF 0x3f3f3f3f
using namespace std;
const int my_max = 1e6 + 10;

char s1[my_max], s2[my_max];
int my_next[my_max];

int my_kmp()
{
    int len1 = strlen(s1), len2 = strlen(s2), ans = 0;
    for (int i = 1, j = 0; i < len1; ++ i)
    {
        while (j > 0 && s1[i] != s1[j]) j = my_next[j];
        if (s1[i] == s1[j]) ++ j;
        my_next[i + 1] = j;
    }
    for (int i = 0, j = 0; i < len2; ++ i)
    {
        while (j > 0 && s1[j] != s2[i]) j = my_next[j];
        if (s1[j] == s2[i]) ++ j;
        if (j == len1) ++ ans, j = my_next[j];
    }
    return ans;
}

int main()
{
    int t;
    scanf("%d", &t);
    memset(my_next, 0, sizeof(my_next));
    while (t --)
    {
        scanf("%s", s1);
        scanf("%s", s2);
        printf("%d
", my_kmp());
    }
    return 0;
}