Oulipo（KMP之子串个数）

àì夳堔傛蜴生んèń 2022-06-09 11:06 130阅读 0赞

# Oulipo #

**Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)  
Total Submission(s): 15695    Accepted Submission(s): 6204**

Problem 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：求出母串中包含多少个子串

#include <cstdio>
    #include <cstring>
    using namespace std;
    char str[10001];
    int ans;
    char str1[1000005];
    int next[10005];
    void getnext(int len)
    {
        int i = 0,k=-1;
        next[0] = -1;
        while(i<len)
        {
            if(k== -1 || str[i] == str[k])
            {
                i++;
                k++;
                next[i] = k;
            }
            else
                k = next[k];
        }
    }
    void KMP(char s[],char t[])
    {
        int i=0,j=0;
        int len1=strlen(s);
        int len2=strlen(t);
        while(i<len2)
        {
            if(j==-1||s[j]==t[i])
            {
                ++i;
                ++j;
            }
            else
                j=next[j];
            if(j==len1)
            {
                ans++;
                j=next[j];//只要找到了就加一,并且不返回即可;
            }
        }
    }
    int main()
    {
        int n;
        scanf("%d",&n);
        while(n--)
        {
            ans=0;
            memset(next,0,sizeof(next));
            scanf("%s",str);
            scanf("%s",str1);
            int len = strlen(str);
            getnext(len);
            KMP(str,str1);
            printf("%d\n",ans);
        }
        return 0;
    }