POJ 3349-Snowflake Snow Snowflakes-字符串哈希

哈希后，对每片雪花对比6次。

#include <cstdio>
#include <cstring>
#include <vector>
#include <iostream>
#include <algorithm>

using namespace std;

const int maxn = 15010;
const int prime = 14997;

struct flake
{
    int arm[6];
    bool operator == (const struct flake b) const
    {
        for(int i=0;i<6;i++)
        {
            int j;
            for(j=0;j<6;j++)
            {
                if(arm[(j+i)%6] != b.arm[j]) break;
            }
            if(j == 6) return true;
        }
        for(int i=0;i<6;i++)
        {
            int j;
            for(j=0;j<6;j++)
            {
                if(arm[(j+i)%6] != b.arm[(6+(-1*j))%6]) break;
            }
            if(j == 6) return true;
        }
        return false;
    }
};

struct flake hashtable[maxn][100];

int Hash(struct flake a)
{
    int ans=0;
    for(int i=0;i<6;i++)
    {
        ans += a.arm[i]%prime;
    }
    return ans%prime;
}

int N;
int conf[maxn];

int main()
{
    while(~scanf("%d",&N))
    {
        flake sn;
        int flag = 0;
        memset(conf,0,sizeof conf);
        for(int i=0;i<N;i++)
        {
            for(int i=0;i<6;i++) scanf("%d",&sn.arm[i]);
            if(flag) continue;
            int key = Hash(sn);
            //printf("key=%d
",key);

            for(int i=0;i<conf[key];i++)
            {
                if(hashtable[key][i] == sn) flag = 1;
            }
            if(!flag) hashtable[key][conf[key]++] = sn;

        }
        if(flag) printf("Twin snowflakes found.
");
        else     printf("No two snowflakes are alike.
");
    }
}