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 = 999983;

struct Snow
{
    int leg[6];
}snow[100000];

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 = 0, j; i < 6; i++)
    {
        if(a.leg[i] == b.leg[0])
        {
            for(j = 0; j < 6; j++)
            {
                if(a.leg[(i+j)%6] != b.leg[j])
                    break;
            }
            if(j >= 6)return 1;
        }
    }
    return 0;
}

bool counterclockwise(const struct Snow &a, const struct Snow &b)
{
    for(int i = 0, j; i < 6; i++)
    {
        if(a.leg[i] == b.leg[5])
        {
            for(j = 0; j < 6; j++)
            {
                if(a.leg[(i+j)%6] != b.leg[5-j])
                    break;
            }
            if(j >= 6)return 1;
        }
    }
    return 0;
}

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 1;
            else p = p->next;
        }
        p = new HashTable;
        p->data = snow_ptr;
    }
    return 0;
}

int main()
{
    int n, key;
    while(scanf("%d", &n) != EOF)
    {
        bool ok = 0;
        memset(Hash, 0, sizeof(Hash));
        for(int i = 0; i < n; i++)
        {
            key = 0;
            for(int j = 0; j < 6; j++)
            {
                scanf("%d", &snow[i].leg[j]);
                key += snow[i].leg[j];
            }
            key %= prime;
            if(!ok)
            {
                ok = hash_insert(key, &snow[i]);
            }
        }
        printf("%s
", ok ? "Twin snowflakes found." : "No two snowflakes are alike.");
    }
    return 0;
}