Oulipo HDU - 1686

Posted 2020-11-14 qldabiaoge

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. 

InputThe 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. 
OutputFor 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


不会kmp的我mmp 
网上的题解全是kmp  
我觉得hash暴力也应该也行

实践证明 暴力hash是可以的

 1 #include <stdio.h>
 2 #include <string.h>
 3 #include <iostream>
 4 #include <algorithm>
 5 #include <vector>
 6 #include <queue>
 7 #include <set>
 8 #include <map>
 9 #include <string>
10 #include <math.h>
11 #include <stdlib.h>
12 #include <time.h>
13 using namespace std;
14 typedef unsigned long long ull;
15 const int maxn = 1e4 + 10;
16 const int seed = 13331;
17 ull HASH, s[maxn*100], p[maxn*100];
18 char a[maxn], b[maxn*100], ans[maxn*100];
19 void init() {
20     p[0] = 1;
21     for (int i = 1 ; i < maxn ; i++)
22         p[i] = p[i - 1] * seed;
23 }
24 int main() {
25     init();
26     int t;
27     scanf("%d", &t);
28     while(t--) {
29         scanf("%s%s", a, b );
30         int lena = strlen(a), lenb = strlen(b);
31         HASH = 0;
32         for (int i = 0 ; i < lena ; i++)
33             HASH = HASH * seed + a[i];
34         int top = 0;
35         s[0] = 0;
36         int sum = 0;
37         for (int i = 0 ; i < lenb ; i++) {
38             ans[top++] = b[i];
39             s[top] = s[top - 1] * seed + b[i];
40             if ( top >= lena && s[top] - s[top - lena]*p[lena] == HASH ) sum++;
41         }
42         printf("%d
", sum);
43     }
44     return 0;
45 }