【poj3461】Oulipo

最新推荐文章于 2019-08-09 10:46:38 发布

转载最新推荐文章于 2019-08-09 10:46:38 发布 · 47 阅读

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原文链接：http://www.cnblogs.com/liumengyue/p/5494631.html

本文介绍了一种字符串匹配算法——KMP算法，并通过一个具体的编程实例展示了如何使用该算法来解决字符串匹配的问题。文章中详细解释了KMP算法的工作原理及其实现过程。

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

Source

BAPC 2006 Qualification

题解

题目意思：求a串在b串出现的次数

直接kmp

#include<iostream>
#include<cstdio>
#include<cstring>
#define N 1000010
using namespace std;
int fail[N],f[N],kmp;
int main()
{
    freopen("oulipo.in","r",stdin);
    freopen("oulipo.out","w",stdout);
    int T;
    scanf("%d",&T);
    for (int I= 1;I<=T;I++)
    {
        int ans = 0;
        char s1[N],s2[N];
           scanf("%s%s",s2+1,s1+1);
        int l1=strlen(s1+1),l2=strlen(s2+1);
      //    cout<<l1<<endl<<l2<<endl;
        fail[1] = 0;
        for (int i=2;i<=l2;i++)
        {
            int p = fail[i-1];
            while (p && s2[p+1] !=s2[i]) p=fail[p];
            if (s2[p+1] == s2[i]) p++;
            fail[i] = p;
        }
        int p=0;
        for (int i=1;i<=l1;i++)
        {
            while (p && s2[p+1] != s1[i]) p=fail[p];
            if (s2[p+1] == s1[i]) p++;
            f[i] = p;
            if (p == l2)
            {
                ans++;
               // printf("%d",i-l2+1);
                //break;
            }
        }
    //    for (int i=1;i<=l2;i++) 
    //    printf("%d ",fail[i]);printf (" \n");
    //    for (int i=1;i<=l1;i++) printf("%d ",f[i]);
        printf("%d\n",ans);
    }
}

转载于:https://www.cnblogs.com/liumengyue/p/5494631.html