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  • 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
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