【POJ3461】Oulipo

题面

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

题解

这是一道KMP模板题
我竟然Wa了N遍才AC（实测N=4）

题目大意：给你T组字符串，问第一个串在第二个中出现了几次

KMP太毒了，，，，老是写Wa。。。。
滑稽
这一道题用来复习KMP

#include<iostream>#include<cstdio>#include<cstdlib>#include<cstring>#include<cmath>#include<algorithm>using namespace std;#define Next ntchar a[1000100],b[1000100];int nt[1000100];inline void getnext()//获得字符串s的next数组{    int l=strlen(a),t;    Next[0]=-1;//如果在0位置失配则是向下移动一位    for(int i=1;i<l;++i)//依次求解后面的next数组    {        t=Next[i-1];        while(a[t+1]!=a[i]&&t>=0)            t=Next[t];        if(a[t+1]==a[i])            Next[i]=t+1;        else            Next[i]=-1;    }}int KMP(){       int l=strlen(b);       int l2=strlen(a);        int i=0,j=0;//匹配指针        int sum=0;       while(i<l)       {               if(a[j]==b[i])               {                     j++;i++;                     if(j==l2)//匹配完了                     {                            ++sum;                            j=nt[j-1]+1;                     }               }               else//失配                {                     if(j==0)//首位失配                           i++;                     else//跳转                         j=nt[j-1]+1;                }       }       return sum;}int main(){    int T;    cin>>T;    while(T--)    {        scanf("%s",a);        scanf("%s",b);        //memset(nt,0,sizeof(nt));        getnext();        cout<<KMP()<<endl;    }    return 0;}