Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 59573		Accepted: 23116

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

Solution

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

typedef long long ll;
const int maxn = 1e6 + 10;
const int maxm = 1e4 + 10;
int nxt[maxm];
char a[maxn], b[maxm];

void getNext(const char* s, int len)
{
    memset(nxt, 0, sizeof(nxt));
    for (int i = 2, j = 0; i <= len; i++)
    {
        while (j && s[i] != s[j + 1]) j = nxt[j];
        if (s[i] == s[j + 1]) j++;
        nxt[i] = j;
    }
}

int kmp(const char* a, const char* b, int n, int m)
{
    getNext(b, m);
    int i, j, cnt = 0;
    for (i = 1, j = 0; i <= n; i++)
    {
        while (j && a[i] != b[j + 1]) j = nxt[j];
        if (a[i] == b[j + 1]) j++;
        if (j == m) cnt++;
    }
    return cnt;
}

int main()
{
    int t;
    scanf("%d", &t);
    while (t--)
    {
        scanf("%s%s", b + 1, a + 1);
        int n = (int)strlen(a + 1), m = (int)strlen(b + 1);
        printf("%d\n", kmp(a, b, n, m));
    }
    return 0;
}

来源：CSDN

作者：SDUWH_2U

链接：https://blog.csdn.net/qq_35850147/article/details/104109999

标签

算法