poj3461 Oulipo【KMP】

Topic link ：

​ ​http://poj.org/problem?id=3461​​

The main idea of the topic ：

Give a string T, To express an article , Give me another string W, Means the word .T and W All contain only 26 Capital letters .

Now calculate words W In the article T Is the number of times .W stay T The number of occurrences in must match continuously , No two matches are possible

There are overlapping parts .

Ideas ：

First find the string W Of Next[] The pointer , And then match , When a match is successful , Keep going back to Next[j] Go backwards

matching , Until the string T At the end of . here , The number of successful matches obtained is the desired , namely W stay T Is the number of times .

AC Code ：

Log in and copy

      
      

       
       #include<iostream>
       
       

       
       #include<algorithm>
       
       

       
       #include<cstdio>
       
       

       
       #include<cstring>
       
       

       
       using 
       
       namespace 
       
       std;
       
       

       
       const 
       
       int 
       
       MAXN 
       
       = 
       
       1000010;
       
       

       
       

       
       char 
       
       T[
       
       MAXN],
       
       W[
       
       MAXN];
       
       

       
       int 
       
       Next[
       
       MAXN],
       
       len1,
       
       len2;
       
       

       
       

       
       void 
       
       GetNext()
       
       
{
       
       
    
       
       int 
       
       i 
       
       = 
       
       0,
       
       j 
       
       = 
       
       -
       
       1;
       
       
    
       
       Next[
       
       0] 
       
       = 
       
       -
       
       1;
       
       
    
       
       while(
       
       i 
       
       < 
       
       len2)
       
       
    {
       
       
        
       
       if(
       
       j 
       
       == 
       
       -
       
       1 
       
       || 
       
       W[
       
       i] 
       
       == 
       
       W[
       
       j])
       
       
        {
       
       
            
       
       i
       
       ++;
       
       
            
       
       j
       
       ++;
       
       
            
       
       Next[
       
       i] 
       
       = 
       
       j;
       
       
        }
       
       
        
       
       else
       
       
            
       
       j 
       
       = 
       
       Next[
       
       j];
       
       
    }
       
       
}
       
       

       
       

       
       int 
       
       KMP()
       
       
{
       
       
    
       
       len1 
       
       = 
       
       strlen(
       
       T);
       
       
    
       
       len2 
       
       = 
       
       strlen(
       
       W);
       
       
    
       
       GetNext();
       
       
    
       
       int 
       
       i 
       
       = 
       
       0,
       
       j 
       
       = 
       
       0;
       
       
    
       
       int 
       
       Ans 
       
       = 
       
       0;
       
       
    
       
       while(
       
       i 
       
       < 
       
       len1)
       
       
    {
       
       
        
       
       if(
       
       j 
       
       == 
       
       -
       
       1 
       
       || 
       
       T[
       
       i] 
       
       == 
       
       W[
       
       j])
       
       
            
       
       i
       
       ++,
       
       j
       
       ++;
       
       
        
       
       else
       
       
            
       
       j 
       
       = 
       
       Next[
       
       j];
       
       
        
       
       if(
       
       j 
       
       == 
       
       len2)
       
       
        {
       
       
            
       
       Ans
       
       ++;
       
       
            
       
       j 
       
       = 
       
       Next[
       
       j];
       
       
        }
       
       
    }
       
       
    
       
       return 
       
       Ans;
       
       
}
       
       

       
       

       
       int 
       
       main()
       
       
{
       
       
    
       
       int 
       
       N;
       
       
    
       
       cin 
       
       >> 
       
       N;
       
       
    
       
       while(
       
       N
       
       --)
       
       
    {
       
       
        
       
       cin 
       
       >> 
       
       W 
       
       >> 
       
       T;
       
       
        
       
       int 
       
       ans 
       
       = 
       
       KMP();
       
       
        
       
       cout 
       
       << 
       
       ans 
       
       << 
       
       endl;
       
       
    }
       
       

       
       
    
       
       return 
       
       0;
       
       
}
      
      
      
      

       
       
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