Hash poj2002 Squares

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#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <algorithm>

#include <cmath>

#include <stack>

#include <queue>

#include <vector>

#include <map>

#include <string>

#include <iostream>

const
int INF = 9973;

const
int kk = 1007;

struct
Node

{

    int
x;int y; int
hash_val;

}node[INF][100];

int
Abs(int
x)

{

    return
x>0?x:-x;

}

int
get_hash(Node &a)

{

    a.hash_val= a.x*a.y+a.y*kk;

    return
a.hash_val = Abs(a.hash_val)%INF;

}

int
Hash(int
x,int y)

{

    return
Abs(x*y+y*kk)%INF;

}

int
len[INF];

void
Insert(Node a)

{

    int
val=get_hash(a);

    for(int
i=0;i<len[a.hash_val];i++)

        if(node[val][i].x==a.x&&node[val][i].y==a.y)

        return
;

    node[val][len[a.hash_val]++]=a;

}

int
match(int 
x,int y)

{

    int
hash1=Hash(x,y);

    for(int
i=0;i<len[hash1];i++)

        if(node[hash1][i].x==x&&node[hash1][i].y==y)

        return
1;

    return
0;

}

int
main()

{

    int
n;

    Node a[20000];

    while(scanf("%d",&n),n){

        memset(node,0,sizeof(node));

        memset(len,0,sizeof(len));

        for(int
i=0;i<n;i++){

            scanf("%d%d",&a[i].x,&a[i].y);

            int
val=get_hash(a[i]);

            Insert(a[i]);

        }

        int
ans=0;

        for(int
i=0;i<n;i++){

            for(int
j=i+1;j<n;j++){

                int
x1=a[i].x-a[i].y+a[j].y;int
y1=a[i].y-a[j].x+a[i].x;

                int
x2=a[j].x+a[j].y-a[i].y;int
y2=a[j].y-a[j].x+a[i].x;

                int
x3=a[i].x-a[j].y+a[i].y;int
y3=a[i].y-a[i].x+a[j].x;

                int
x4=a[j].x-a[j].y+a[i].y;int
y4=a[j].y+a[j].x-a[i].x;

                if(match(x1,y1)&&match(x2,y2))

                    ans++;

                if(match(x3,y3)&&match(x4,y4))

                    ans++;

            }

        }

        printf("%d\n",ans/4);

    }

    return
0;

}