HDU 1686 Oulipo（优化的KMP）

Oulipo

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 17441    Accepted Submission(s): 6938

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

#include <iostream>
#include<cstdio>
#include<string>
#include<cstring>
int next[10001], num;
char a[1000001], b[10001];
int lena, lenb;
void  get_next()//自身和自身比较，找某种特征
{
    int i, j;
    i = 0; next[0] = -1; j = -1;
    while (i<lenb)
    {
        if (j == -1 || b[i] == b[j])//匹配成功的话，继续下一位
        {
            i++;
            j++;
            if (b[i] == b[j])
            {
                next[i] = next[j];
            }
            else
            {
                next[i] = j;
            }
        }
        else//否则返回到可以匹配的位置 
        {
            j = next[j];
        }
    }
}
void index_KMP()
{
    int i, j;
    i = 0;
    j = 0;
    num = 0;
    while (i<lena)
    {
        if (a[i] == b[j] || j == -1) //进行两个字符串的匹配  
        {
            i++;//匹配成功，往后继续匹配  
            j++;
        }
        else//匹配完成一次，代表出现了一次，记录下来
        {
            j = next[j];
        }
        if (j == lenb)//匹配失败，寻找数组中可以匹配的位置  
        {
            num++;
            j = next[j];
        }
    }
    printf("%d
", num);
}
int main()
{
    int n;
    while (scanf("%d", &n) != EOF)
    {
        getchar();
        while (n--)
        {
            gets(b);
            gets(a);
            lena = strlen(a);
            lenb = strlen(b);
            get_next();
            index_KMP();
        }
    }
    return 0;
}