POJ 2513, Colored Sticks

Time Limit: 5000MS  Memory Limit: 128000K
Total Submissions: 13696  Accepted: 3384

Description
You are given a bunch of wooden sticks. Each endpoint of each stick is colored with some color. Is it possible to align the sticks in a straight line such that the colors of the endpoints that touch are of the same color?

 

Input
Input is a sequence of lines, each line contains two words, separated by spaces, giving the colors of the endpoints of one stick. A word is a sequence of lowercase letters no longer than 10 characters. There is no more than 250000 sticks.

 

Output
If the sticks can be aligned in the desired way, output a single line saying Possible, otherwise output Impossible.

 

Sample Input
blue red
red violet
cyan blue
blue magenta
magenta cyan

 

Sample Output
Possible

 

Hint
Huge input,scanf is recommended.

 

Source
The UofA Local 2000.10.14

---

//  POJ2513.cpp : Defines the entry point for the console application.
//

#include  < iostream >
using   namespace  std;

// Tries
struct  Trie
{
    Trie():id( - 1 ),end( false ){memset(next,  0 ,  sizeof (next));}
     int  id;
     bool  end;
    Trie *  next[ 26 ];
};
static   int  num  =   0 ;
int  GetID( char   * x, Trie *  root)
{
    Trie  * temp  =  root;
     for  ( int  i  =   0 ; i  <  strlen(x);  ++ i)
    {
         if  (temp -> next[x[i] - ' a ' ]  ==  NULL)
            temp -> next[x[i] - ' a ' ]  =   new  Trie;
        temp  =  temp -> next[x[i] - ' a ' ];
    }
     if  (temp -> end) return  temp -> id;
    temp -> end  =   true ;
    temp -> id  =  num ++ ;
     return  temp -> id;
}

// Disjoint set
int  Find( int  x,  int  f[])
{
     if (x  !=  f[x])
         return  f[x]  =  Find(f[x], f);
     return  f[x];
};
void  Union( int  x, int  y,  int  f[])
{
    f[Find(x, f)]  =  f[Find(y, f)];
};

int  main( int  argc,  char *  argv[])
{
    Trie root;
     char  w[ 30 ], w1[ 12 ], w2[ 12 ];
     int  degree[ 500001 ];
    memset(degree, 0 , sizeof (degree));
     int  f[ 500001 ];
     for ( int  i  =   0 ; i  <   500001 ;  ++ i) f[i]  =  i;
    
     // create Trie tree
     while  (gets(w)  &&  w[ 0 ]  !=   0 )
    {
        sscanf(w, " %s %s " , w1, w2);
         int  x  =  GetID(w1,  & root);
         int  y  =  GetID(w2,  & root);
         ++ degree[x];
         ++ degree[y];
        Union(x,y,f);
    }

     // check odd points
     int  odd  =   0 ;
     for  ( int  i  =   0 ; i  <  num;  ++ i)
         if  (degree[i]  &   1   !=   0 )  ++ odd;

     // check connected
     int  x  =  Find( 1 ,f);
     for  ( int  i  =   0 ; i  <  num ;  ++ i)
         if  (x  !=  Find(i,f))
        {
            odd  =   - 1 ;
             break ;
        };    

     if  (odd  ==   0   ||  odd  ==   2 ) cout  <<   " Possible "   <<  endl;
     else  cout  <<   " Impossible "   <<  endl;
     return   0 ;
}