hdu 1686 Oulipo kmp算法

题目地址：http://acm.hdu.edu.cn/showproblem.php?pid=1686

 

题目：

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

 

 

思路：裸的kmp应用。

#include <bits/stdc++.h>
#define PB push_back
#define MP make_pair
using namespace std;
typedef long long LL;
typedef pair<int,int> PII;
#define PI acos((double)-1)
#define E exp(double(1))
#define K 1000000+9
int nt[10000+1];
char a[K],b[10001];
//参数为模板串和next数组
//字符串均从下标0开始
void kmp_next(char *T,int *nt)
{
    nt[0]=0;
    for(int i=1,j=0,m=strlen(T);i<m;i++)
    {
        while(j&&T[i]!=T[j])j=nt[j-1];
        if(T[i]==T[j])j++;
        nt[i]=j;
    }
}
int kmp(char *S,char *T,int *nt)
{
    kmp_next(T,nt);
    int ans=0,sn=strlen(S),tn=strlen(T);
    for(int i=0,j=0;i<sn;i++)
    {
        while(j&&S[i]!=T[j])j=nt[j-1];
        if(S[i]==T[j])j++;
        if(j==tn)
            ans++;
    }
    return ans;
}
int main(void)
{
    int t;cin>>t;
    while(t--)
    {
        scanf("%s%s",b,a);
        printf("%d\n",kmp(a,b,nt));
    }

    return 0;
}