Look here. It's my code!
Pz. find good tests for it!
//1215_SB
#include <iostream>
#include <cmath>
using namespace std;
#define eps 0.000001
struct Point{
// ....};
inline double triangle_S(Point& pa, Point& pb, Point& pc){
//calculates square of truiangle...
}
inline long double min_dist_to_line(Point& A, Point& B, Point& C)
{
    //here are a big and fat bug :)
    Point S;
    S.x = (B.x + A.x)/2.0;
    S.y = (B.y + A.y)/2.0;
    long double res = 0.0;
    long double a = C.dist(A);
    long double b = C.dist(B);
    long double d = A.dist(B);
    long double s = C.dist(S);

    if((s < a)&&(s < b))
    {
        res = sqrt(a*a - ((a*a - b*b + d*d)/(2.0*d))*((a*a - b*b + d*d)/(2.0*d)));
    }
    else
        res = (a > b) ? b : a;
    return res;

}
Point a[103];
int main()
{
    int n, i;
//getting the data
    double S_of_target = 0.0;
    for (int i = 1; i <= n; i++)
    {
        S_of_target += triangle_S(Dolly, a[i], a[i+1]);
    }
    double S_of_target_from_Center = 0.0;
    for (int i = 1; i <= n; i++)
    {
        S_of_target_from_Center += triangle_S(Center, a[i], a[i+1]);
    }
    if (fabs(S_of_target_from_Center - S_of_target) < eps)
    {
        printf("0.000\n");
        return 0;
    }

    long double min = 9999999999999999999999.9;
    for(i = 1; i <= n; i++)
    {
    //////////////////////////////////
        double d_t_l = min_dist_to_line(a[i], a[i+1], Center);
        if(min - d_t_l > eps)
        {
            min = d_t_l;
        }
        /////////////////////
    }
    printf("%.3lf\n", 2.0*min);

    return 0;
}

Edited by author 23.02.2007 15:37