private void btnTinh5_Click(object sender, EventArgs e)
{
try
{
Stopwatch time = new Stopwatch();
string input = txtInput5.Text;
string[] coordinates = input.Split(' ');
n=coordinates.Length-1;
diem = new diem[n];
int i = 0;
time.Start();
foreach (string s in coordinates)
{
if (i >= n)
{
break;
}
string[] coord = s.Split(',');
diem[i++] = new diem(int.Parse(coord[0]), int.Parse(coord[1]));
//i++;
}
closestpair closest = new closestpair();
float d = closest.ClosestPair(diem, i);
time.Stop();
txtKetQua5.Text = d.ToString();
textBox1.Text = time.Elapsed.Milliseconds.ToString();
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
public float BruteForce(diem[] a, int n)
{
float d = float.MaxValue;
for (int i = 0; i < n - 1; i++)
{
for (int j = i + 1; j < n; j++)
{
if (KhoangCach(a[i], a[j]) < d)
{
d = KhoangCach(a[i], a[j]);
}
}
}
return d;
}
public static float KhoangCach(diem diem1, diem diem2)
{
return (float)Math.Sqrt((diem1.x - diem2.x) * (diem1.x - diem2.x) + (diem1.y - diem2.y) * (diem1.y - diem2.y));
}
private bool IfExist(diem b,int vt)
{
for (int i = 0; i < vt; i++)
{
if (diem[i].x == b.x && diem[i].y == b.y)
{
return true;
}
}
return false;
}
private void button7_Click(object sender, EventArgs e)
{
if (String.IsNullOrEmpty(txtNhap5.Text))
{
MessageBox.Show("Vui lòng nhập n");
return;
}
//tạo bộ test ngẫu nhiên
txtInput5.Text = "";
n = int.Parse(txtNhap5.Text);
diem = new diem[n];
Random rand = new Random();
for (int i = 0; i < n; i++)
{
diem[i] = new diem(rand.Next(n), rand.Next(n));
if (IfExist(diem[i], i))
{
continue;
}
txtInput5.Text += diem[i].ToString() + " ";
}
}
private void mergeY(diem[] result, diem[] left, diem[] right)
{
int i1 = 0; // index into left array
int i2 = 0; // index into right array
for (int i = 0; i < result.Length; i++)
{
if (i2 >= right.Length || (i1 < left.Length && left[i1].y <= right[i2].y))
{
result[i] = left[i1]; // take from left
i1++;
}
else
{
result[i] = right[i2]; // take from right
i2++;
}
}
}
// Returns the second half of the given array.
private diem[] rightHalf(diem[] a)
{
int size1 = a.Length / 2;
int size2 = a.Length - size1;
diem[] right = new diem[size2];
for (int i = 0; i < size2; ++i)
{
right[i] = a[i + size1];
}
return right;
}
// Rearranges the elements of a into sorted order using
// the merge sort algorithm (recursive).
private void mergeSortY(diem[] a)
{
if (a.Length >= 2)
{
// split array into two halves
diem[] left = leftHalf(a);
diem[] right = rightHalf(a);
// sort the two halves
mergeSortY(left);
mergeSortY(right);
// merge the sorted halves into a sorted whole
mergeY(a, left, right);
}
}
private diem[] leftHalf(diem[] a)
{
int size1 = a.Length / 2;
diem[] left = new diem[size1];
for (int i = 0; i < size1; ++i)
{
left[i] = a[i];
}
return left;
}
private float KhoangCach(diem diem1, diem diem2)
{
return (float)Math.Sqrt((diem1.x - diem2.x) * (diem1.x - diem2.x) + (diem1.y - diem2.y) * (diem1.y - diem2.y));
}
private float Closest(diem[] p, diem[] q, int l, int r)
{
if ((r - l) <= 3)
{
return BruteForce(p, r - l);
}
else
{
int mid = l + (r-l) / 2;
float dl = Closest(p, q, l, mid);
float dr = Closest(p, q, mid + 1, r);
float dmin = Math.Min(dl, dr);
int num = 0;
diem[] temp = new diem[r - l];
float min = dmin * dmin;
for (int k = l; k < r; k++)
{
if (Math.Abs(q[k].x - p[mid].x) < dmin)
{
temp[num++] = q[k];
}
}
for (int i = 0; i < num - 1 ; i++)
{
int j = i + 1;
while ((j < num ) && ((temp[j].y - temp[i].y) * (temp[j].y - temp[i].y) < min))
{
min = Math.Min(KhoangCach(temp[j], temp[i]) * KhoangCach(temp[j], temp[i]), min);
j++;
}
}
return (float)Math.Sqrt(min);
}
}
public float ClosestPair(diem[] diem, int n)
{
mergeSortX(diem);
diem[] p = diem;
mergeSortY(diem);
diem[] q = diem;
float min = Closest(p, q, 0, n);
return min;
}
