POJ 3461 （KMP）

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

题意：在S串里找T串出现多少次？

题解：直接上KMP模板就可以了

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int ans;
#define N 1000000+5
char s1
,s2
;
int fail
;
void getfail(char *p,int *f)
{
int m=strlen(p);
f[0]=0;
f[1]=0;
for(int i=1;i<m;i++)
{
int j=f[i];
while(j&&p[i]!=p[j])j=f[j];
f[i+1]=p[i]==p[j]?j+1:0;
}
}
void find(char *t,char *p,int *f)
{
int n=strlen(t),m=strlen(p);
getfail(p,f);
int j=0;
for(int i=0;i<n;i++)
{
while(j&&p[j]!=t[i])j=f[j];
if(p[j]==t[i])j++;
if(j==m)ans++;
}
}
int main()
{
#ifdef CDZSC
freopen("i.txt","r",stdin);
#endif
int tt;
scanf("%d",&tt);
while(tt--)
{
scanf("%s%s",s1,s2);
ans=0;
find(s2,s1,fail);
printf("%d\n",ans);
}
return  0;
}