Cod sursa(job #2227948)

Utilizator georgerapeanuRapeanu George georgerapeanu Data 2 august 2018 11:53:53
Problema Cele mai apropiate puncte din plan Scor 60
Compilator cpp Status done
Runda Arhiva educationala Marime 5.69 kb
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <vector>
#include <cassert>
   
using namespace std;
   
struct point_data_t{
    double x,y;
      
    point_data_t(){
        x = y = 0;
    }
      
    point_data_t(double x,double y){
        this->x = x;
        this->y = y;
    }
      
    double sqr_len(){
        return x * x + y * y; 
    }
      
    double len(){
        return sqrt(sqr_len());
    }
      
    point_data_t operator - (point_data_t &other)const{
        return point_data_t(x - other.x,y - other.y);
    }
      
    bool operator < (const point_data_t &other)const{
        if(x != other.x){
            return x < other.x;
        }
        return y < other.y;
    }
      
    bool operator == (const point_data_t &other)const{
        return x == other.x && y == other.y;
    }
      
    bool operator != (const point_data_t &other)const{
        return x != other.x || y != other.y;
    }
};
  
  
class KDTree{
private:
    KDTree *leftson,*rightson;
    point_data_t P;
public:
      
    KDTree(){
        leftson = rightson = NULL;
        P = point_data_t(0,0);
    }
      
    ~KDTree(){
        if(leftson != NULL){
            delete leftson;
        }
          
        if(rightson != NULL){
            delete rightson;
        }
    }
      
    KDTree(KDTree *leftson,KDTree *rightson,point_data_t P){
        this->leftson = leftson;
        this->rightson = rightson;
        this->P = P;
    }
      
    void build(vector<point_data_t> &points,int left,int right);
      
        ///best_dist_so_far contains the actual distance squared;leaves P uneffected,returns the closeste point
    point_data_t find_nearest_neighbour(point_data_t &P,double &best_dist_so_far);
      
    KDTree(vector<point_data_t> points);
};
  
void KDTree::build(vector<point_data_t> &points,int left,int right){///[left,right);swaps x and y of points to prevent two compare functions;changes the order of parameter points
	int mid = (left + right) / 2;
	nth_element(points.begin() + left,points.begin() + mid,points.begin() + right);
	  
	this->P = points[mid];
	  
	for(int i = left;i < right;i++){
		swap(points[i].x,points[i].y);
	}
	  
	if(left < mid){
		this->leftson = new KDTree;
		this->leftson->build(points,left,mid);
	}
	  
	if(mid + 1 < right){
		this->rightson = new KDTree;
		this->rightson->build(points,mid + 1,right);
	}
	  
	for(int i = left;i < right;i++){
		swap(points[i].x,points[i].y);
	}
}

point_data_t KDTree::find_nearest_neighbour(point_data_t &P,double &best_dist_so_far){///P has the coordonates in order for this depth,returns the answer with coordinates swaped depending on the depth
	  
	point_data_t best_subtree_point = this->P;
	  
	if(P != this->P && best_dist_so_far > (this->P - P).sqr_len()){
		best_dist_so_far = (this->P - P).sqr_len();
		best_subtree_point = this->P;
	}
	  
	if(leftson == NULL && rightson == NULL){
		return best_subtree_point;
	}
	  
	if(leftson == NULL){
		  
		swap(P.x,P.y);
		point_data_t rightson_ans = this->rightson->find_nearest_neighbour(P,best_dist_so_far);
		swap(P.x,P.y);
		swap(rightson_ans.x,rightson_ans.y);
		  
		if((P - best_subtree_point).sqr_len() > (P - rightson_ans).sqr_len()){
			best_subtree_point = rightson_ans;
		}
		return best_subtree_point;
	}
	  
	if(rightson == NULL){
		swap(P.x,P.y);
		point_data_t leftson_ans = this->leftson->find_nearest_neighbour(P,best_dist_so_far);
		swap(P.x,P.y);
		swap(leftson_ans.x,leftson_ans.y);
		  
		if((P - best_subtree_point).sqr_len() > (P - leftson_ans).sqr_len()){
			best_subtree_point = leftson_ans;
		}
		return best_subtree_point;
	}           
	  
	if(P < this->P){
		swap(P.x,P.y);
		point_data_t leftson_ans = this->leftson->find_nearest_neighbour(P,best_dist_so_far);
		swap(P.x,P.y);
		swap(leftson_ans.x,leftson_ans.y);
		  
		if((P - best_subtree_point).sqr_len() > (P - leftson_ans).sqr_len()){
			best_subtree_point = leftson_ans;
		}
		  
		if(P.x + sqrt(best_dist_so_far) >= this->P.x){
			swap(P.x,P.y);
			point_data_t rightson_ans = this->rightson->find_nearest_neighbour(P,best_dist_so_far);
			swap(P.x,P.y);
			swap(rightson_ans.x,rightson_ans.y);
			  
			if((P - best_subtree_point).sqr_len() > (P - rightson_ans).sqr_len()){
				best_subtree_point = rightson_ans;
			}
		}
		return best_subtree_point;
	}
	else{
		swap(P.x,P.y);
		point_data_t rightson_ans = this->rightson->find_nearest_neighbour(P,best_dist_so_far);
		swap(P.x,P.y);
		swap(rightson_ans.x,rightson_ans.y);
		  
		if((P - best_subtree_point).sqr_len() > (P - rightson_ans).sqr_len()){
			best_subtree_point = rightson_ans;
		}
		  
		if(P.x - sqrt(best_dist_so_far) <= this->P.x){
			swap(P.x,P.y);
			point_data_t leftson_ans = this->leftson->find_nearest_neighbour(P,best_dist_so_far);
			swap(P.x,P.y);
			swap(leftson_ans.x,leftson_ans.y);
			  
			if((P - best_subtree_point).sqr_len() > (P - leftson_ans).sqr_len()){
				best_subtree_point = leftson_ans;
			}
		}
		return best_subtree_point;
	}
}

KDTree::KDTree(vector<point_data_t> points){
	this->build(points,0,(int)points.size());
}
  
int N;
vector<point_data_t> V;
FILE *f = fopen("cmap.in","r");
FILE *g = fopen("cmap.out","w");
   
int main(){
   
    fscanf(f,"%d",&N);
    V.resize(N);
    for(int i = 0;i < N;i++){
        fscanf(f,"%lf %lf",&V[i].x,&V[i].y);
    }
       
    KDTree *root = new KDTree(V);
    double ans = 5e18;
	
    for(auto it:V){
		double tmp = 5e18;
        root->find_nearest_neighbour(it,tmp);
		ans = min(tmp,ans);
    }
       
    fprintf(g,"%.7f",sqrt(ans));
       
    fclose(f);
    fclose(g);
       
    return 0;
}