Cod sursa(job #2067678)

Utilizator IonLiviuRebreanuMoartea lu Florica IonLiviuRebreanu Data 16 noiembrie 2017 19:00:02
Problema Cele mai apropiate puncte din plan Scor 45
Compilator cpp Status done
Runda Arhiva educationala Marime 1.93 kb
#include<iostream>
#include<fstream>
#include<cmath>
#include<algorithm>
#include<iomanip>

using namespace std;

ifstream f("cmap.in");
ofstream g("cmap.out");

#define Nmax 100010
#define Inf 1<<30

struct punct
{
    int x, y;
}v[Nmax],w[Nmax];

int n;

bool cmp (punct a, punct b)
{
    if(a.x == b.x)
        return a.y < b.y;
    return a.x < b.x;
}

bool cmpy(punct a, punct b)
{
    return a.y < b.y;
}

double dist ( punct a, punct b)
{
    double difx = a.x - b.x;
    double dify = a.y - b.y;

    return sqrt ( difx * difx + dify * dify ) ;
}


double divide ( int st, int dr)
{
    if( dr - st == 1)
        return dist( v[st], v[dr] );
    else
    if ( dr-st == 2 )
    {
        double D, Dmin=Inf;
        int i, j;

        for(i = st; i < dr; i++)
            for(j = i + 1 ; j <= dr; j++)
            {
                D = dist( v[i] , v[j] );
                if(D < Dmin)
                    Dmin = D;
            }
        return Dmin;
    }

    int m=( st + dr ) / 2;
    double S1 = divide ( st, m ) ;
    double S2 = divide ( m+1, dr ) ;

    int d = v[m].x;

    double S = S1;
    if(S2 < S1)
        S = S2;

    int i,j = m+1 ,k=0;

    double delta = ceil(sqrt(d));

    for( i = st; i <= dr; i++)
    {
        if( abs( v[i].x - d ) <= delta )
        {
            w[k].x = v[i].x;
            w[k].y = v[i].y;
            k++;
        }
    }

    sort(w,w+k,cmpy);

    double D, Dmin=Inf;

    for(i = 0; i < k ; i++)
        for(j = i + 1 ; j <= (i+7) && j < k; j++)
        {
            D = dist(w[i],w[j]);
            if(D < Dmin)
                Dmin=D;
        }
    if(Dmin > S)
        Dmin = S;

    return Dmin;
}

int main()
{
    int n;
    f >> n;

    for ( int i = 1; i <= n ;i++)
        f >> v[i].x >> v[i].y;

    sort(v+1,v+n+1,cmp);

    g << fixed << setprecision(6) << divide(1,n);
    return 0;
}