POJ 3461 Oulipo【KMP，子串出现次数，可重叠】

2023年2月2日 344次阅读 来源: KMP算法

Oulipo

Time Limit: 1000MS Memory Limit: 65536K
Total Submissions: 36896 Accepted: 14896

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

原题链接：http://poj.org/problem?id=3461

题意：输入两个字符串，问第一个字符串在第二个字符串中的出现次数。（可重叠）。

直接套模板：

AC代码：

#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
const int maxn=100000+5;
char p[maxn];
char s[maxn*100];
int lenp,lens;
int Next[maxn];
void getNext()
{
    int i=0,j=-1;
    memset(Next,0,sizeof(Next));
    Next[0]=-1;
    while(i<lenp)
    {
        if(j==-1||p[i]==p[j])
        {
            i++,j++;
            Next[i]=j;
        }
        else
            j=Next[j];
    }
}
int KMP()
{
    int i=0,j=0;
    int ans=0;
    while(i<lens)
    {
        if(j==-1||s[i]==p[j])
        {
            i++,j++;
        }
        else
            j=Next[j];
        if(j==lenp)
        {
            ans++;
            j=Next[j];
            //若两个不同的匹配没有交集则j=0,
            //若存在交集则j=next[j];
        }
    }
    return ans;
}
int main()
{
    int T;
    cin>>T;
    while(T--)
    {
        cin>>p>>s;
        lens=strlen(s);
        lenp=strlen(p);
        getNext();
        cout<<KMP()<<endl;
    }
    return 0;
}

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    原文作者：KMP算法
    原文地址: https://blog.csdn.net/hurmishine/article/details/52841993
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