hdu1686 KMP 求在字符串A中字符串B出现的次数

Posted 2021-01-23 -citywall123

Oulipo

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 24592    Accepted Submission(s): 9516

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

 

//HD1686
#include<iostream>
#include<algorithm>
#include<stdio.h>
#include<string.h>
using namespace std;
const int N = 1000005;
int i, n, m, t, sum;
char T[N], P[N];//P[]是需要比较的字符串，T[]是被比较的字符串
int next1[N];

void getnext(char  *P, int *next1)
{
    int j = 0;
    int k = -1;
    next1[0] = -1;
    while (j<m)
    {
        if (k == -1 || P[j] == P[k])
        {
            next1[++j] = ++k;
        }
        else
        {
            k = next1[k];
        }
    }
}
int KMP(char *T, char *P)
{
    sum = 0;
    int i = 0;
    int j = 0;
    getnext(P, next1);
    while (i<n&&j<m)//注意这里的等号要不要取
    {        
        if (j == -1 || T[i] == P[j])//匹配的情况，坐标后移
        {
            i++;
            j++;
        }
        else//如果不匹配
        {
            j = next1[j];
        }
        if (j == m)//判断是否匹配结束
        {
            sum++;
        }
    }
    return sum;
}
int main()
{
    scanf("%d", &t);
    for (int i = 0; i<t; i++)
    {        
        scanf("%s%s", T, P);
        m = strlen(P);
        n = strlen(T);
        printf("%d
", KMP(T, P));
    }
    //system("pause");
    return 0;
}