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

3BAPCBAPCAZAAZAZAZAVERDIAVERDXIVYERDIAN

Sample Output

130

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+5char s1[N],s2[N];int fail[N];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 CDZSCfreopen("i.txt","r",stdin);#endifint tt;scanf("%d",&tt);while(tt--){scanf("%s%s",s1,s2);ans=0;find(s2,s1,fail);printf("%d\n",ans);}return  0;}