poj3461 KMP

Oulipo

Time Limit: 1000MS Memory Limit: 65536KTotal Submissions: 34604 Accepted: 13980

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

3BAPCBAPCAZAAZAZAZAVERDIAVERDXIVYERDIAN

Sample Output

130

题意：给出一个字符串，求在另外一个字符串中出现的次数

#include<stdio.h>#include<string.h>#include<algorithm>using namespace std;char a[10005],b[1000005];int nexta[10005];void getnext(){    int len=strlen(a);    nexta[0]=-1;    int k=-1;    int j=0;    while(j<len)    {        if(k==-1||a[j]==a[k]){            ++j;            ++k;            if(a[j]!=a[k])                nexta[j]=k;            else                nexta[j]=nexta[k];        }        else            k=nexta[k];    }}int kmp(){    int len_a=strlen(a);    int len_b=strlen(b);    int count=0;    int j=0;    int i=0;    while(j<len_b){        if(i==-1||a[i]==b[j]){            i++;            j++;        }        else            i=nexta[i];        if(i==len_a){            count++;            i=nexta[i];        }    }    return count;}int main(){    int n;    scanf("%d",&n);    while(n--)    {        scanf("%s%s",a,b);        getnext();        int temp=kmp();        printf("%d\n",temp);    }    return 0;}