POJ 3461 Oulipo (求模式串在文本串中出现的次数)

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 36128		Accepted: 14584

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

/*
 * POJ 3461 Oulipo
 * 求模式串在文本串中出现的次数
 *
 * KMP套版题，可看前一篇转载的博客，对KMP讲的很详细
 */
#include <stdio.h>
#include <string.h>
#include <iostream>
using namespace std;

const int MAXN = 1000000+10;
const int MAXM = 10000+10;

void Get_Next(char* P,int* next)
{
    int i=0,k=-1;
    int plen=strlen(P);
    next[0]=-1;
    while(i<plen)
    {
        if(k==-1||P[k]==P[i])
        {
            next[++i]=++k;
        }
        else k=next[k];
    }
}
int KMP_count(char* T,char* P,int* next)
{
    int ans=0;
    int i=0,j=0;
    int tlen=strlen(T);
    int plen=strlen(P);
    while(i<tlen)
    {
        //如果j=-1，或者当前字符匹配成功(即S[i] == P[j],继续往后匹配
        if(j==-1||T[i]==P[j])
        {
            i++,j++;
        }
        else
        {
            //失配了，根据next数组往后移动
            j=next[j];
        }
        //如果此时P的匹配长度等于了原有长度，说明出现了一次，答案加1
        //并且跳回前一步继续进行匹配
        if(j==plen)
        {
            ans++;
            j=next[j];
        }
    }
    return ans;
}
char W[MAXM],T[MAXN];
int nxt[MAXM];

int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%s%s",W,T);
        Get_Next(W,nxt);
        printf("%d
",KMP_count(T,W,nxt));
    }
    return 0;
}