Data commit

Task/Convex-hull/FreeBASIC/convex-hull.basic

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+#include "crt.bi"
+Screen 20
+Window (-20,-20)-(30,30)
+
+Type Point
+    As Single x,y
+    As Long done
+End Type
+
+#macro rotate(pivot,p,a,scale)
+Type<Point>(scale*(Cos(a*.0174533)*(p.x-pivot.x)-Sin(a*.0174533)*(p.y-pivot.y))+pivot.x, _
+scale*(Sin(a*.0174533)*(p.x-pivot.x)+Cos(a*.0174533)*(p.y-pivot.y))+pivot.y)
+#endmacro
+
+
+Dim As Point p(1 To ...)={(16,3),(12,17),(0,6),(-4,-6),(16,6),(16,-7),(16,-3),(17,-4),(5,19), _
+(19,-8),(3,16),(12,13),(3,-4),(17,5),(-3,15),(-3,-9),(0,11),(-9,-3),(-4,-2),(12,10)}
+
+
+Function south(p() As Point,Byref idx As Long) As Point
+    Dim As Point s=Type(0,100)
+    For n As Long=Lbound(p) To Ubound(p)
+        Circle(p(n).x,p(n).y),.2,7,,,,f
+        If s.y>p(n).y Then s=p(n):idx=n
+    Next n
+    Return s
+End Function
+
+Function segment_distance(lx1 As Single, _
+                          ly1 As Single, _
+                          lx2 As Single, _
+                          ly2 As Single, _
+                          px As Single,_
+                          py As Single, _
+                          Byref ox As Single=0,_
+                          Byref oy As Single=0) As Single
+    Dim As Single M1,M2,C1,C2,B
+    B=(Lx2-Lx1):If B=0 Then B=1e-20
+    M2=(Ly2-Ly1)/B:If M2=0 Then M2=1e-20
+    M1=-1/M2
+    C1=py-M1*px
+    C2=(Ly1*Lx2-Lx1*Ly2)/B
+    Var L1=((px-lx1)*(px-lx1)+(py-ly1)*(py-ly1)),L2=((px-lx2)*(px-lx2)+(py-ly2)*(py-ly2))
+    Var a=((lx1-lx2)*(lx1-lx2) + (ly1-ly2)*(ly1-ly2))
+    Var a1=a+L1
+    Var a2=a+L2
+    Var f1=a1>L2,f2=a2>L1
+    If f1 Xor f2 Then
+        Var d1=((px-Lx1)*(px-Lx1)+(py-Ly1)*(py-Ly1))
+        Var d2=((px-Lx2)*(px-Lx2)+(py-Ly2)*(py-Ly2))
+        If d1<d2 Then Ox=Lx1:Oy=Ly1 : Return Sqr(d1) Else  Ox=Lx2:Oy=Ly2:Return Sqr(d2)
+    End If
+    Var M=M1-M2:If M=0 Then M=1e-20
+    Ox=(C2-C1)/(M1-M2)
+    Oy=(M1*C2-M2*C1)/M
+    Return Sqr((px-Ox)*(px-Ox)+(py-Oy)*(py-Oy))
+End Function
+
+
+Dim As Long idx
+Var s= south(p(),idx)
+p(idx).done=1
+Redim As Point ans(1 To 1)
+ans(1)=s
+Dim As Point e=s
+e.x=1000
+Dim As Long count=1
+Dim As Single z
+Circle(s.x,s.y),.4,5
+
+Do
+    z+=.05
+    Var pt=rotate(s,e,z,1)
+    For n As Long=Lbound(p) To Ubound(p)
+        If segment_distance(s.x,s.y,pt.x,pt.y,p(n).x,p(n).y)<.05  Then
+            s=p(n)
+            If p(n).done=0 Then
+                count+=1
+                Redim Preserve ans(1 To count)
+                ans(count)=p(n)
+                p(n).done=1
+            End If
+        End If
+        Circle(s.x,s.y),.4,5
+    Next n
+Loop Until z>360
+
+For n As Long=Lbound(ans) To Ubound(ans)
+    printf (!"(%2.0f , %2.0f )\n", ans(n).x, ans(n).y)
+Next
+Sleep