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 Input3BAPCBAPCAZAAZAZAZAVERDIAVERDXIVYERDIANSample Output130

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;}