vb三点求圆，多点求外接圆。

概述'本程序运行时耗时约为5-7秒。 '以前在vb版回复问题时编写。   VBScript code Option Explicit Private Type mypoint     x As Double     y As Double End Type Dim p(0

      '本程序运行时耗时约为5-7秒。        '以前在vb版回复问题时编写。                         VBScript code             
Option Explicit    Private Type mypoint    x As Double    y As Double  End Type    Dim p(0 To 49) As mypoint  Dim smallcx As Double  Dim smallcy As Double  Dim smallr As Double    Private Sub Form_Load()    '开始时将smallr都置成很大    smallr = 1E+90  End Sub    Private Function equ(ByVal a As Double,ByVal b As Double) As Boolean    If Abs(a - b)  < 0.000001 Then      equ = True    Else      equ = False    End If  End Function    Private Function Is_Three_Point_In_A_line(ByVal x1 As Double,ByVal y1 As Double,ByVal x2 As Double,ByVal y2 As Double,ByVal x3 As Double,ByVal y3 As Double) As Boolean    Dim a As Double,b As Double,e As Double        a = (x1 + x2) * (x1 - x2) + (y1 + y2) * (y1 - y2)    b = (x3 + x2) * (x3 - x2) + (y3 + y2) * (y3 - y2)    e = (x1 - x2) * (y3 - y2) - (x2 - x3) * (y2 - y1)      Is_Three_Point_In_A_line = equ(e,0)    End Function    Private Sub Calc_TPC(ByVal x1 As Double,ByVal y3 As Double,cx As Double,cy As Double,r As Double)    Dim a As Double,e As Double      a = (x1 + x2) * (x1 - x2) + (y1 + y2) * (y1 - y2)    b = (x3 + x2) * (x3 - x2) + (y3 + y2) * (y3 - y2)    e = (x1 - x2) * (y3 - y2) - (x2 - x3) * (y2 - y1)      cx = (a * (y3 - y2) + b * (y2 - y1)) / (2 * e)    cy = (a * (x2 - x3) + b * (x1 - x2)) / (2 * e)    r = Sqr((x1 - cx) * (x1 - cx) + (y1 - cy) * (y1 - cy))          End Sub    Private Function incircle(ByVal cx As Double,ByVal cy As Double,ByVal r As Double,ByVal px As Double,ByVal py As Double) As Boolean    Dim l1 As Double,l2 As Double        l1 = px - cx    l2 = py - cy        If Sqr(l1 * l1 + l2 * l2)  <= r Then      incircle = True    Else      incircle = False    End If      End Function  Private Sub Command1_Click()    Cls        Randomize Timer        Dim i As Long,j As Long,k As Long    Dim l As Long    Dim cx As Double,r As Double    Dim count As Long        '先生成50个点，并显示在屏幕上    For i = 0 To 49      p(i).x = Rnd * 2000      p(i).y = Rnd * 2000      Me.Circle (p(i).x,p(i).y),15,vbRed    Next i        '计算所有的圆    For i = 0 To 49      For j = 0 To 49        For k = 0 To 49          If Not Is_Three_Point_In_A_line(p(i).x,p(i).y,p(j).x,p(j).y,p(k).x,p(k).y) Then            '三点可求圆                        '求圆            Calc_TPC p(i).x,p(k).y,cx,cy,r                        '计算所有的点是否在圆内            count = 0            For l = 0 To 49              If incircle(cx,r,p(l).x,p(l).y) Then                count = count + 1              End If            Next l                        If count = 50 Then              '所有的点都在圆内              If r  < smallr Then                smallcx = cx                smallcy = cy                smallr = r              End If            End If          End If        Next k      Next j    Next i        '画出最小的圆    Circle (smallcx,smallcy),smallr,vbGreen  End Sub
               
           
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