给出一些正方形，让你求这些正方形顶点之间的最大距离的平方。

//返回点集直径的平方
int diameter2(vector
  
    & points) {
    vector
   
     p = ConvexHull(points); int n = p.size(); if(n==1) return 0; if(n==2) return Dist2(p[0], p[1]); p.push_back(p[0]); int ans = 0; for(int u = 0, v = 1; u < n; ++u) { for(;;) { int diff = Cross(p[u+1]-p[u], p[v+1]-p[v]); if(diff<=0) { ans = max(ans, Dist2(p[u], p[v])); if(diff==0) ans = max(ans, Dist2(p[u], p[v+1])); break; } v = (v+1) % n; } } return ans; }