poj3461(KMP)

Oulipo

Time Limit: 1000MS Memory Limit: 65536KTotal Submissions: 17587 Accepted: 7059

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 wordW and a textT, count the number of occurrences of W inT. All the consecutive characters of W must exactly match consecutive characters ofT. 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 stringW).
• 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 wordW in the textT.

Sample Input

3BAPCBAPCAZAAZAZAZAVERDIAVERDXIVYERDIAN

Sample Output

130

Source

BAPC 2006 Qualification

 

本题说了很多，要求模式串在主串中出现的次数。

运用KMP算法，再一次匹配成功后不退出，滑动模式串开始下一次匹配，总的效率不错。

 

#include<iostream>#include<cstdio>#include<cstring>using namespace std;char W[10010],T[1000010];//W为模式串，T为主串int next[10010];//KMP算法中计算next[]数组void getNext(char *p){    int j,k,len=strlen(p);    j=0;    k=-1;    next[0]=-1;    while(j<len)    {        if(k==-1||p[j]==p[k])        {            next[++j]=++k;        }        else k=next[k];    }}//KMP算法统计模式串W在主串T中出现的次数int KMP_count(char *W,char *T){    int i,wlen=strlen(W),tlen=strlen(T),j=0,ans=0;    getNext(W);    for(i=0;i<tlen;i++)    {        while(j>0&&T[i]!=W[j])          j=next[j];        if(W[j]==T[i])j++;        if(j==wlen)        {            ans++;            j=next[j];        }    }    return ans;}int main(){    int tcase;    scanf("%d",&tcase);    while(tcase--)    {        scanf("%s%s",&W,&T);        strlen(W);        strlen(T);        printf("%d\n",KMP_count(W,T));    }    return 0;}