HDU 1686 Oulipo

最新推荐文章于 2021-12-11 18:48:23 发布

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B - Oulipo

Time Limit:1000MS Memory Limit:32768KB 64bit IO Format:%I64d & %I64u

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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

KMP字符串匹配，题目前面说了一大堆有的没的，题意就是给一个T,和一个W，问在T里有几个能匹配到W。
用KMP算法，当匹配串长度匹配到m的时候，ans++;然后输出ans就行了。下一次匹配的时候从nxt数组对应的位置开始。

#include <stdio.h>
#include <string.h>
#define T 1000005
#define W 10005
char t[T],w[W];
int nxt[W];
int n,m;
void getnext(){
    int j, k;
    j = 0; k = -1; nxt[0] = -1;
    while(j<m){
        if (k==-1 || w[j]==w[k]){
            nxt[++j] = ++k;
        }
        else{
            k = nxt[k];
        }
    }
}
int kmp(){
    getnext();
    int ans=0;
    int j, k;
    j = 0; k = 0;
    while(j<n){
        if (k==-1 || w[k]==t[j]){
            ++k;++j;
        }
        else{
            k = nxt[k];
        }
         if(k==m)
        {
                k=nxt[k];
                ans++;
        }
    }
    return ans;
}
int main()
{
        int c;
        scanf("%d",&c);
        while(c--)
        {
                scanf("%s",w);
                scanf("%s",t);
                n=strlen(t);
                m=strlen(w);
                printf("%d\n",kmp());
        }
        return 0;
}