Cod sursa(job #1295871)

Utilizator radu_uniculeu sunt radu radu_unicul Data 20 decembrie 2014 12:49:59
Problema Cele mai apropiate puncte din plan Scor 0
Compilator cpp Status done
Runda Arhiva educationala Marime 2.37 kb
#include<fstream>
#include <float.h>
#include <stdlib.h>
#include <math.h>
#include<iomanip>
using namespace std;
ifstream fin("cmap.in");
ofstream fout("cmap.out");
int a;
struct Point
{
    int x, y;
};
int compareX(const void* a, const void* b)
{
    Point *p1 = (Point *)a,  *p2 = (Point *)b;
    return (p1->x - p2->x);
}
int compareY(const void* a, const void* b)
{
    Point *p1 = (Point *)a,   *p2 = (Point *)b;
    return (p1->y - p2->y);
}
float dist(Point p1, Point p2)
{
    return sqrt( (p1.x - p2.x)*(p1.x - p2.x) +
                 (p1.y - p2.y)*(p1.y - p2.y)
               );
}
float bruteForce(Point P[], int n)
{
    float min = FLT_MAX;
    for (int i = 0; i < n; ++i)
        for (int j = i+1; j < n; ++j)
            if (dist(P[i], P[j]) < min)
                min = dist(P[i], P[j]);
    return min;
}
float min(float x, float y)
{
    return (x < y)? x : y;
}
float stripClosest(Point strip[], int size, float d)
{
    float min = d;
    for (int i = 0; i < size; ++i)
        for (int j = i+1; j < size && (strip[j].y - strip[i].y) < min; ++j)
            if (dist(strip[i],strip[j]) < min)
                min = dist(strip[i], strip[j]);

    return min;
}
float closestUtil(Point Px[], Point Py[], int n)
{
    if (n <= 3)
        return bruteForce(Px, n);
    int mid = n/2;
    Point midPoint = Px[mid];
    Point Pyl[mid+1];
    Point Pyr[n-mid-1];
    int li = 0, ri = 0;
    for (int i = 0; i < n; i++)
    {
      if (Py[i].x <= midPoint.x)
         Pyl[li++] = Py[i];
      else
         Pyr[ri++] = Py[i];
    }
    float dl = closestUtil(Px, Pyl, mid);
    float dr = closestUtil(Px + mid, Pyr, n-mid);
    float d = min(dl, dr);
    Point strip[n];
    int j = 0;
    for (int i = 0; i < n; i++)
        if (abs(Py[i].x - midPoint.x) < d)
            strip[j] = Py[i], j++;
    return min(d, stripClosest(strip, j, d) );
}
float closest(Point P[], int n)
{
    Point Px[n];
    Point Py[n];
    for (int i = 0; i < n; i++)
    {
        Px[i] = P[i];
        Py[i] = P[i];
    }

    qsort(Px, n, sizeof(Point), compareX);
    qsort(Py, n, sizeof(Point), compareY);
    return closestUtil(Px, Py, n);
}
int main()
{
    fin>>a;
    Point P[a];
    for(int i=0;i<a;i++) fin>>P[i].x>>P[i].y;
    int n = sizeof(P) / sizeof(P[0]);
    fout <<  setprecision(8)<<closest(P, n);
    return 0;
}