HDU 1686 求子串的数量

Oulipo
Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%I64d
& %I64u
 HDU
1686

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

 

KMP基础

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
using namespace std;

int nex[10005];
void pre(string str){
int len=str.size();
nex[0]=-1;
int i=0,j=-1;
while(i<len){
if(j==-1||str[i]==str[j]){
i++;j++;
nex[i]=j;
}else
j=nex[j];
}
}
int kmp(string str1,string str2){
pre(str1);
int ans=0;
int len1=str1.size(),len2=str2.size(),i=0,j=0;
while(i<len2&&j<len1){
if(j==-1||str1[j]==str2[i]){
i++;
j++;
}else
j=nex[j];
if(j==len1){
ans++;
j=nex[j];
}
}
return ans;
}
int main()
{
std::cout.sync_with_stdio(false);
string str1,str2;
int n;
cin>>n;
while(n--){
cin>>str1>>str2;
cout<<kmp(str1,str2)<<endl;
}
}