#include <algorithm>
#include <cstdio>
using namespace std;
structnode
{
int x, y;
} p[1005];
bool Greater(const structnode &a, const structnode &b)
{
if (a.x == b.x)
return a.y < b.y;
else
return a.x < b.x;
}
int main()
{
int T,i,j,sum;
node p1, p2;
while ( scanf("%d", &T)!=EOF && T )
{
sum = 0;
for (i = 0; i < T; ++i)
scanf("%d%d", &p[i].x , &p[i].y);
sort(p, p + T, Greater);
for (i = 0; i < T; i++)
for (j = i + 1; j < T; j++)
{
if (p[i].y>=p[j].y) //重复的正方形不要
{
p1.x = p[i].x + p[j].y - p[i].y;
p1.y = p[i].y + p[i].x - p[j].x;
p2.x = p[j].x + p[j].y - p[i].y;
p2.y = p[j].y + p[i].x - p[j].x;
if (!binary_search(p, p+T, p1, Greater)) //看看计算出来的点是否在已经排好的点集中存在
continue;
if (!binary_search(p, p+T, p2, Greater))
continue;
sum++;
}
}
printf("%d\n", sum );
}
return 0;
}
poj Squares(stl 二分查找 + sort)