POJ - 3461 （kmp）

题目链接：http://poj.org/problem?id=3461

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 49608		Accepted: 19699

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

 

题目大意：输入t，代表t组样例，每个样例有两个字符串，求第一个字符串在第二个字符串中出现的次数

思路：可以说是kmp的裸题，注意的是kmp好多题目都卡cin，都要用scanf才不会超时

看代码：

#include<iostream>
#include<string.h>
#include<map>
#include<cstdio>
#include<cstring>
#include<stdio.h>
#include<cmath>
#include<ctype.h>
#include<math.h>
#include<algorithm>
#include<set>
#include<queue>
typedef long long ll;
using namespace std;
const ll mod=1000;
const int maxn=1e6+10;
const int maxk=5e3+10;
const int maxx=1e4+10;
const ll maxe=1000+10;
#define INF 0x3f3f3f3f3f3f
#define Lson l,mid,rt<<1
#define Rson mid+1,r,rt<<1|1
int next[maxn];
void cal_next(char a[])
{
    int len=strlen(a);
    next[0]=-1;
    int k=-1;
    for(int i=1;i<len;i++)
    {
        while(k>-1&&a[k+1]!=a[i])
        {
            k=next[k];
        }
        if(a[k+1]==a[i]) k++;
        next[i]=k;
    }
}
void kmp(char a[],char b[])
{
    int k=-1,sum=0;
    int len1=strlen(a);
    int len2=strlen(b);
    for(int i=0;i<len2;i++)
    {
        while(k>-1&&a[k+1]!=b[i])
        {
            k=next[k];
        }
        if(a[k+1]==b[i]) k++;
        if(k==len1-1)
        {
            sum++;
            k=next[k];
        }
    }
    printf("%d\n",sum);
    //cout<<sum<<endl;
}
int main()
{
    //string a,b;
    char a[maxn],b[maxn];
    int t;
    //cin>>t;
    scanf("%d",&t);
    while(t--)
    {
        //cin>>a>>b;
        scanf("%s",a);
        getchar();
        scanf("%s",b);
        cal_next(a);
        kmp(a,b);
    }
    return 0;
}