HDU 1686 Oulipo（kmp）

Oulipo

Time Limit: 3000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 16525 Accepted Submission(s): 6617

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

用str首字符与buf首字符比较，两种情况，如下
①如果从str首字符一直比到str尾字符都一样，则计数器+1，然后将str首字符移至buf第二个字符
②如果从str首字符开始比，中途有一个不匹配，则str首字符向buf的下一个字符移动，
重复上述两个动作，直到str首位移至buf的L2-L1-1位为止；

直接kmp模板吧

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxx=1e6+10;
int Next[maxx];
char s[maxx],p[maxx];
int len1,len2;
void getnext()
{
    int i=0,j=-1;
    Next[0]=-1;
    while(i<len1)
    {
        if(j==-1||p[i]==p[j])
        {
            ++i;
            ++j;
            if(p[i]==p[j])
                Next[i]=Next[j];
            else
                Next[i]=j;
        }
        else
            j=Next[j];
    }
}
void getkmp()
{
    int num=0,i=0,j=0;
    while(i<len2)
    {
        if(j==-1|s[i]==p[j])
        {
            ++i;++j;
            if(j==len1)
                num++;
        }
        else
            j=Next[j];

    }
    printf("%d\n",num);
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%s%s",p,s);
        len1=strlen(p);
        len2=strlen(s);
        getnext();
        getkmp();
    }
    return 0;
}