B - Oulipo HDU - 1686

痛定思痛。 2022-04-17 04:50 93阅读 0赞

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

tips:题目大意就是让你找出一个字符串中有多少个给定的字串，kmp的一个变形应用吧；

代码：

#include<bits/stdc++.h>
    using namespace std;
    int ne[1123456];
    char a[1123456],b[1123456];
    int cnt;
    void GetNext(char a[])
    {
        memset(ne,0,sizeof(ne));
        int i=0,j=-1;
        ne[0]=-1;
        int len=strlen(a);
        while(i<len){
            if(j==-1||a[i]==a[j])
                ne[++i]=++j;
            else
                j=ne[j];
        }
    }
    void Kmp(char a[],char b[])
    {
        int len1=strlen(a);
        int len2=strlen(b);
        int i=0,j=0;
        while(i<len2)
        {
            if(j==-1||a[j]==b[i])
            {
                i++;
                j++;
            }
            else
                j=ne[j];
          if(j==len1)
                {
                  cnt++;
                  j=ne[j];
                }
        }
    }
    int main()
    {
    
        int l,t;
        scanf("%d ",&t);
        while(t--)
        {
            scanf("%s %s",a,b);
            cnt=0;
            GetNext(a);
            Kmp(a,b);
            cout<<cnt<<endl;
        }
    }