Oulipo 【KMP求字串在主串中的个数板子】

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

BAPC

AZA

AZAZAZA

VERDI

AVERDXIVYERDIAN

Sample Output

基本算是模板，看代码即可：

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<math.h>
#include<map>
#include<queue>
#include<vector>
#include<stack>
#define inf 0x3f3f3f3f
using namespace std;
typedef long long ll;
const int N=1000005;

char s[N],t[N];
int nex[N];//记录最长后缀
int l1,l2;

void get_next()
{
    int i=0,j=-1;
    nex[0]=-1;
    while(i<l2)
    {
        if(j==-1||t[i]==t[j])
            nex[++i]=++j;
        else
            j=nex[j];
    }
}

int kmp()
{
    memset(nex,0,sizeof(nex));
    get_next();
    int i=0,j=0,ans=0;
    while(i<l1)
    {
        if(j==-1||s[i]==t[j])
        {
            i++;
            j++;
        }
        else
            j=nex[j];
        if(j>=l2)//只需要在模板上加上这一步即可
            ans++;
    }
    return ans;
}

int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        int i,j;
        scanf("%s%s",t,s);
        l1=strlen(s);//主串长度
        l2=strlen(t);//子串长度
        printf("%d\n",kmp());
    }
    return 0;
}

Oulipo 【KMP求字串在主串中的个数 板子】

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Oulipo 【KMP求字串在主串中的个数板子】