Oulipo kmp

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B - Oulipo

The French author Georges Perec (1936�C1982) 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


 1 //
 2 //  main.cpp
 3 //  pat
 4 //
 5 //  Created by dada on 2017/3/6.
 6 //  Copyright © 2017年 dada. All rights reserved.
 7 //
 8 
 9 #include<iostream>
10 #include<string.h>
11 #include<stdio.h>
12 #include<string>
13 
14 using namespace std;
15 
16 char a[10005],b[1000005];
17 int nexta[10005];
18 
19 void getNext()
20 {
21     nexta[0]=-1;
22     int i = 0,j = -1,lena=strlen(a);
23     while(i < lena)
24     {
25         if(j==-1 || a[i]==a[j])
26         {
27             i++,j++;
28             nexta[i]=j;
29         }
30         else
31             j=nexta[j];
32         
33     }
34 }
35 
36 int solve()
37 {
38     int i = 0,j = 0,ans=0,lenb=strlen(b),lena=strlen(a);
39     while(i<lenb)
40     {
41         if(j==-1 || a[j]==b[i])
42         {
43             if(j==lena-1)
44             {
45                 //i=i-nexta[j],j=0; 这样写TLE
46                 ans++;
47                 j=nexta[j];
48             }
49             else
50                 i++,j++;
51         }
52         else
53             j=nexta[j];
54     }
55     return ans;
56 }
57 int main()
58 {
59     int t;
60     scanf("%d",&t);
61     while(t--)
62     {
63         scanf("%s%s",&a,&b);
64         getNext();
65         printf("%d
",solve());
66     }
67     return 0;
68 }

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原文地址:https://www.cnblogs.com/Xycdada/p/6518879.html