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最新推荐文章于 2024-10-04 22:22:29 发布

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最新推荐文章于 2024-10-04 22:22:29 发布

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原文链接：http://www.cnblogs.com/france/p/4808747.html

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#include <iostream>
#include <cmath>
#include <map>
using namespace std;
const int prime=1999;

struct point{
int x,y;
}p[1001];

struct hashtable{
int value;
map<int,int> mymap;
}myhash[prime];

void setHash(int x,int y){
	int h= (x*x+y*y) % prime; 
	myhash[h].value=1;
	myhash[h].mymap.insert(pair<int, int>(x, y));


}
bool Search(int x,int y)  
{	map<int,int>::iterator ptr;
	
    int h = (x*x+y*y) % prime;  
	if(myhash[h].value!=1)return false;
	ptr=myhash[h].mymap.find(x);
	int tt=(*ptr).second;
	if(tt==y)return true;
    return false;
}  
int work(int n){
	int i,j;
	int sum=0;
 for(i=1;i<n;i++)
	 for(j=i+1;j<=n;j++)
	 {
			int x1 = p[i].x - (p[i].y - p[j].y);  
            int y1 = p[i].y + (p[i].x - p[j].x);  
            int x2 = p[j].x - (p[i].y - p[j].y);  
            int y2 = p[j].y + (p[i].x - p[j].x);  
            if(Search(x1,y1) && Search(x2,y2)) sum++;  
			
	 
	 }
	 for(i=1;i<n;i++)
		 for(j=i+1;j<=n;j++){
	 int x3 = p[i].x + (p[i].y - p[j].y);  
            int y3 = p[i].y - (p[i].x - p[j].x);  
            int x4 = p[j].x + (p[i].y - p[j].y);  
            int y4 = p[j].y - (p[i].x - p[j].x);  
            if(Search(x3,y3) && Search(x3,y3)) sum++; 
		 }
	 return sum/4;

}
int main(){

int n;

while(1){
	cin>>n;
	if(n==0)break;
	for(int j=0;j<prime;j++){
	myhash[j].value=-1;
	}
	for(int i=1;i<=n;i++){
		cin>>p[i].x>>p[i].y;
		setHash(p[i].x,p[i].y);
	}
	cout<<work(n)<<endl;

}
return 0;
}