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  • hdu1686

    题目意思:找到上串在下串中有多少个

    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
    #include<stdio.h>
    #include<string.h>
    
    int next[10005],lenw,lent;
    char W[10005],T[1000005];
    
    void set_next()
    {
        int i=0,j=-1;
        next[0]=-1;
        lenw=strlen(W);
        while(i<lenw)
        {
            if(j==-1||W[i]==W[j])
            {
                i++;j++;
                next[i]=j;
            }
            else
            j=next[j];
        }
    }
    int KMP()
    {
        int k=0,i=0,j=0;
        lent=strlen(T);
        while(i<lent)
        {
            if(T[i]==W[j]||j==-1)
            {
                i++;j++;
            }
            else
            j=next[j];
            if(j==lenw)
            {
                k++; j=next[j];//表示W的第j个以前都与T的从i-next[j]到第i-1这段已经匹好了
            }                   //next[j]的值是在W[j]前面的串中最长前缀和最长后缀相等,那么
                              //当前的匹配成功,就说明W的第j个以前都与T的从i-next[j]到第i-1这段也已经匹配好了
        }
        return k;
    }
    int main()
    {
        int t;
        scanf("%d",&t);
        while(t--)
        {
            getchar();
            scanf("%s %s",W,T);
            set_next();
                printf("%d
    ",KMP());
        }
    }
    


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  • 原文地址:https://www.cnblogs.com/jiangu66/p/3220287.html
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