HDU 1686 Oulipo [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

题目大意：先给出子串，再给出母串 ，要求子串在母串中的存在个数； 直接KMP ；（注意cin会TLE）

AC代码：

#include <bits/stdc++.h>using namespace std ;char a[1000000+20],b[1000000+20];int pre[1000000+20] , lena , lenb;void getpre(){int i = 0 , j = -1 ;pre[0] = -1;while(i<lenb){if(j==-1||b[i]==b[j]) pre[++i]=++j;else j = pre[j] ;}}int kmp(){int i = 0 , j = 0 , ans = 0 ;getpre();while(i<lena&&j<lenb){if(j==-1||a[i]==b[j]){i++;j++;}else j = pre[j];if(j==lenb)        {            ans++;            j = pre[j] ;        }}return ans ;}int main(){int t;cin>>t;while(t--)    {        scanf("%s %s",b,a);        lenb = strlen(b);        lena = strlen(a);        cout<<kmp()<<endl;    }return 0 ;}