POJ 3349 Snowflake Snow Snowflakes Hash

题目链接： http://poj.org/problem?id=3349

 #include <stdio.h>
 #include <string.h>
 #include <iostream>
 using namespace std;
 const int prime = ;

 struct Snow
 {
     int leg[];
 }snow[];

 struct HashTable
 {
     struct Snow *data;
     struct HashTable *next;
     HashTable()
     {
         next = NULL;
     }
 };

 struct HashTable *Hash[prime];

 bool clockwise(const struct Snow &a, const struct Snow &b)
 {
     for(int i = , j; i < ; i++)
     {
         if(a.leg[i] == b.leg[])
         {
             for(j = ; j < ; j++)
             {
                 if(a.leg[(i+j)%] != b.leg[j])
                     break;
             }
             if(j >= )return ;
         }
     }
     return ;
 }

 bool counterclockwise(const struct Snow &a, const struct Snow &b)
 {
     for(int i = , j; i < ; i++)
     {
         if(a.leg[i] == b.leg[])
         {
             for(j = ; j < ; j++)
             {
                 if(a.leg[(i+j)%] != b.leg[-j])
                     break;
             }
             if(j >= )return ;
         }
     }
     return ;
 }

 bool hash_insert(int key, struct Snow *snow_ptr)
 {
     if(Hash[key] == NULL)
     {
         Hash[key] = new HashTable;
         Hash[key]->data = snow_ptr;
     }
     else
     {
         struct HashTable *p = Hash[key];
         while(p != NULL)
         {
             if(clockwise(*p->data, *snow_ptr) || counterclockwise(*p->data, *snow_ptr))
                 return ;
             else p = p->next;
         }
         p = new HashTable;
         p->data = snow_ptr;
     }
     return ;
 }

 int main()
 {
     int n, key;
     while(scanf("%d", &n) != EOF)
     {
         bool ok = ;
         memset(Hash, , sizeof(Hash));
         for(int i = ; i < n; i++)
         {
             key = ;
             for(int j = ; j < ; j++)
             {
                 scanf("%d", &snow[i].leg[j]);
                 key += snow[i].leg[j];
             }
             key %= prime;
             if(!ok)
             {
                 ok = hash_insert(key, &snow[i]);
             }
         }
         printf("%s\n", ok ? "Twin snowflakes found." : "No two snowflakes are alike.");
     }
     return ;
 }