POJ 3349 (hash)

Snowflake Snow Snowflakes

Time Limit: 4000MS		Memory Limit: 65536K
Total Submissions: 20772		Accepted: 5426

Description

You may have heard that no two snowflakes are alike. Your task is to write a program to determine whether this is really true. Your program will read information about a collection of snowflakes, and search for a pair that may be identical. Each snowflake
has six arms. For each snowflake, your program will be provided with a measurement of the length of each of the six arms. Any pair of snowflakes which have the same lengths of corresponding arms should be flagged by your program as possibly identical.

Input

The first line of input will contain a single integer n, 0 < n ≤ 100000, the number of snowflakes to follow. This will be followed by n lines, each describing a snowflake. Each snowflake will be described by a line containing six
integers (each integer is at least 0 and less than 10000000), the lengths of the arms of the snow ake. The lengths of the arms will be given in order around the snowflake (either clockwise or counterclockwise), but they may begin with any of the six arms.
For example, the same snowflake could be described as 1 2 3 4 5 6 or 4 3 2 1 6 5.

Output

If all of the snowflakes are distinct, your program should print the message:

No two snowflakes are alike.

If there is a pair of possibly identical snow akes, your program should print the message:

Twin snowflakes found.

做了一个很弱的HASH函数，链表没用指针，用的数组实现的，没想到竟然就过了。。。。

hash = sum % 100000

#include<stdio.h>
#include<string.h>
#include<iostream>

#define maxn 200000
#define fuck 100000

struct NODE{
int data,next;
} node[maxn];

int a[maxn][6] = {0},ha[maxn] = {0};

int judge(int k1,int k2)
{
int ar[20],i,j,k,ans;
for(i = 0;i < 6;i++) ar[i] = ar[i+6] = a[k1][i];
for(i = 0;i < 6;i++) {
ans = 1;
for(j = 0;j < 6;j++) if (ar[i+j] != a[k2][j]) ans = 0;
if (ans) return 1;
}
for(i = 0;i < 6;i++) ar[5-i] = ar[5-i+6] = a[k1][i];
for(i = 0;i < 6;i++) {
ans = 1;
for(j = 0;j < 6;j++) if (ar[i+j] != a[k2][j]) ans = 0;
if (ans) return 1;
}
return 0;
}

int hash(int k)
{
int i,sum = 0;
for(i = 0;i < 6;i++) sum = (sum + a[k][i]) % fuck;
return sum;
}

int work(void)
{
int  i,j,n,temp,t,k,l = 1;
memset(node,0,sizeof(node));
scanf("%d",&n);
for(i = 1;i <= n;i++) {
for(j = 0;j <  6;j++) scanf("%d",&a[i][j]);
t = hash(i);
if (ha[t] == 0) {
ha[t] = l;
node[l].data = i;
node[l++].next = 0;
}
else {
temp = ha[t];
while (temp != 0) {
if (judge(node[temp].data,i)) {
printf("Twin snowflakes found.\n");
return 0;
}
else temp = node[temp].next;
}
node[l].next = ha[t];
node[l].data = i;
ha[t] = l++;
}
}
printf("No two snowflakes are alike.\n");
return 0;
}

int main()
{
work();
return 0;
}