做法
bool compare(node s1 , node s2){
if(s1.x / t < s2.x / t) return true;
if(s1.x / t > s2.x / t) return false;
return s1.y < s2.y;
}
bool compare(node s1 , node s2){
if(s1.x / t < s2.x / t) return true;
if(s1.x / t > s2.x / t) return false;
return s1.y < s2.y;
}