最短路径算法源码

时　间:2012-08-21 08:47:36
作　者:ihcn   ID：27115  城市：宁波
摘　要:最短路径算法源码
正　文:

其中a1,b1,c1是以fnode排序生成的数组，a1对应fnode,b1对应tnode,c1对应length,同样a2,b2,c2,是以tnode 生成的数组。Indexa1是对应某一起点与其相连的终点的个数，indexb1时对应某一终点与其相连的起点的个数，即其拓扑关系。
Public Function shortpath(startno As Integer, endno As Integer) As Single
以开始点，结束点为参数。

 
Dim result() As Single
Dim result1 As Integer
定义结果点

 
Dim s1 As Single
Dim min As Single
Dim ii, I, j, aa As Integer
Dim yc() As Boolean
Dim ycd() As Boolean
Dim rs1() As Single
Dim no() As Integer
Dim nopoint As Integer
ReDim yc(1 To maxno) As Boolean
ReDim ycd(1 To maxno) As Boolean
ReDim rs1(1 To maxno) As Single
ReDim result(1 To 2, 1 To maxno) As Single
定义结果，其中result(1,maxno)为结果点，result(2,maxno)为结果长度。

 
For I = 1 To maxno// maxno为网中最大的节点数。
Yc(i) = False //标记已经查过的点。
Ycd(i) = False //标记已经作结果点用过的点
rs1(i) = 1E+38 //假设从起点到任一点的距离都为无穷大
Next I
ll = startno //设置开始点。
Yc(ll) = True //标记开始点为真。即已经作结果点用过。
J = 0
For aa = 1 To maxno
先从与开始点相连的终点寻找

 
For I = 1 To indexa1(2, ll) //以与ll点相连的起点的个数循环
result1 = b1(indexa1(1, ll) - I + 1)找出与LL点相连的终点的点号
s1 = c1(indexa1(1, ll) - I + 1) + result(2, ll)找出长度并求和
If yc(result1) = True Then GoTo 200如果以被经查过进行下一个
If ycd(result1) = True Then//如果已经作为结果点判断哪一个长
If rs1(result1) >= s1 Then//如果这一点到起点的长度比现在的路线长，替代
rs1(result1) = s1
result(1, result1) = ll//设置到这点的最短路径的前一点为LL点（精华部分）
result(2, result1) = s1设置到这点的最短路径长度
GoTo 200
Else
GoTo 200
End If
End If
如果上面的条件都不符合则进行下面的语句

 
ycd(result1) = True
rs1(result1) = s1
result(1, result1) = ll
result(2, result1) = s1
每找到一个点加一，为了下面的判断

 
j = j + 1
ReDim Preserve no(1 To j) As Integer
从新 定义数组并使其值为当前的点号

 
no(j) = result1
200 Next I
再从与开始点相连的终点寻找，与上面一样不再标注

For I = 1 To indexb2(2, ll)
result1 = a2(indexb2(1, ll) - I + 1)
s1 = c2(indexb2(1, ll) - I + 1) + result(2, ll)
If yc(result1) = True Then GoTo 300
If ycd(result1) = True Then
If rs1(result1) >= s1 Then
rs1(result1) = s1
result(1, result1) = ll
result(2, result1) = s1
GoTo 300
Else
GoTo 300
End If
End If
ycd(result1) = True
rs1(result1) = s1
result(1, result1) = ll
result(2, result1) = s1
j = j + 1
ReDim Preserve no(1 To j) As Integer
no(j) = result1
300 Next I

设置最小为无穷大，最短路径点为空

 
min = 1E+38
minpoint = Null
（优化部分）
找出已经查过点中长度最短的点

 
For I = aa To j
If min > rs1(no(i)) Then
ii = I
min = rs1(no(i))
minpoint = no(i)
End If
Next I
如果没有结果，即起点与终点没有通路退出程序

 
If min = 1E+38 Then Exit Function
（重点优化）将两点互换，减少循环。
No(ii) = no(aa)
no(aa) = minpoint
标记已经作为结果点判断过
yc(minpoint) = True
ll = minpoint
判断结果点是否等于终点，如果等于则已经找到最短路径
If minpoint = endno Then Exit For
Next aa
返回最短路径长度
Stpath = result(2, endno)
End Function

最短路径程序

Option Explicit
Dim p(7) As rcd
Dim Matrix(7, 7) As Integer

Private Sub Command2_Click()
End
End Sub

Function seekSmall(a() As Integer)
Dim n, k, m, i, j As Integer
n = UBound(a) - 2
i = 1
m = a(0, 1): k = 0
Do While a(i, 1) <> 0
    If a(i, 1) < m Then
        m = a(i, 1): k = i
    End If
    i = i + 1
Loop
seekSmall = k
Print
End Function

Private Sub cmdContinue_Click()
MsgBox "请输入要求的路径", vbOKCancel
txtStart.Text = "": txtEnd.Text = "": txtStart.SetFocus
txtPath.Text = "": txtLength.Text = ""
End Sub

Private Sub cmdEnd_Click()
End
End Sub

Private Sub cmdOk_Click()
Dim nS, nE As Integer
Dim h As String
Dim i, j As Integer
Dim n As Integer
Dim x, y, z As Integer
If txtStart.Text <> "" And txtEnd.Text <> "" Then
    nS = Val(txtStart.Text) - 1: nE = Val(txtEnd.Text) - 1 '确定起始点
  If (nS > 6 Or nE > 6) Then
        MsgBox "没有该点，请重新输入正确的点", vbOKCancel
    End If
Else
    MsgBox "没有输入"
End If
    p(0).iN = nS  '记录起始点
    n = 0
    For j = 0 To 6
        If j <> nS Then
        p(0).fT(n, 0) = j
        p(0).fT(n, 1) = Matrix(nS, j)
        n = n + 1
        End If
    Next j
    p(0).jN = seekSmall(p(0).fT())
    Print
    p(0).Judge = True
n = 0
For j = 0 To 6
    If (j <> p(0).fT(p(0).jN, 0)) And (j <> nS) Then
        p(0).bT(n, 0) = j
        p(0).bT(n, 1) = Matrix(nS, j)
        n = n + 1
    End If
Next j
For i = 1 To 5
    p(i).iN = p(i - 1).fT(p(i - 1).jN, 0)
    For j = 0 To 5 - i
        If ((p(i - 1).bT(j, 1) >= (p(i - 1).fT(p(i - 1).jN, 1) + Matrix(p(i).iN, p(i - 1).bT(j, 0)))) And ((p(i - 1).fT(p(i - 1).jN, 1)) + Matrix(p(i).iN, p(i - 1).bT(j, 0)) < 100)) Then
            If p(i - 1).bT(j, 0) = nE Then
                If p(i - 1).bT(j, 1) >= (p(i - 1).fT(p(i - 1).jN, 1) + Matrix(p(i).iN, p(i - 1).bT(j, 0))) Then
                p(i).Judge = True
                End If
            End If
            p(i).fT(j, 1) = (p(i - 1).fT(p(i - 1).jN, 1) + Matrix(p(i).iN, p(i - 1).bT(j, 0)))
            p(i).fT(j, 0) = p(i - 1).bT(j, 0)
        Else
            p(i).fT(j, 1) = p(i - 1).bT(j, 1)
            p(i).fT(j, 0) = p(i - 1).bT(j, 0)
        End If
        If p(i).fT(j, 0) = nE Then
        If p(i).fT(j, 1) > 100 Then
            p(i).Judge = True
        End If
        End If
    Next j
    p(i).jN = seekSmall(p(i).fT())
    n = 0
    For j = 0 To 5 - i
        If p(i).jN <> j Then
            p(i).bT(n, 0) = p(i).fT(j, 0)
            p(i).bT(n, 1) = p(i).fT(j, 1)
            n = n + 1
        End If
    Next j
Next i
For i = 0 To 5
    If p(i).iN = nE Then
        For j = 0 To i
       If p(j).Judge = True Then
                h = h & (p(j).iN + 1) & "  "
            End If
        Next j
        txtLength.Text = p(i - 1).fT(nS, 1)
    ElseIf i = 5 And p(i).iN <> nE Then
       For j = 0 To 5
            If p(j).Judge = True Then
                 h = h & (p(j).iN + 1) & "  "
            End If
        Next j
        txtLength.Text = p(5).fT(nS, 1)
    End If
Next i

txtPath.Text = h & nE + 1
'Open "d:\1.txt" For Output As #1
'For z = 0 To 5
'Print #1,
'Print #1, "----------------------------------------------------------";
'Print #1,
'    Print #1, p(z).iN
'    For x = 0 To 5 - z
'        For y = 0 To 1
'        Print #1, p(z).fT(x, y);
'        Next y
'    Next x
'    Print #1,
'    Print #1, p(z).jN
'     For x = 0 To 4 - z
'        For y = 0 To 1
'        Print #1, p(z).bT(x, y);
'        Next y
'    Next x
'Next z
'For x = 0 To 6
'Print #1,
'Print #1, p(x).Judge
'Next x
'Close

End Sub

Private Sub cmdOpen_Click()
Dim i, j As Integer
On Error GoTo a:
With CommonDialog1
    .Filter = "文本文件（*.txt）|*.txt|所有文件（*.*）|*.*"
    .ShowOpen
End With
Open CommonDialog1.FileName For Input As #1
    txtEdit.Text = Input(LOF(1), 1)
Close #1
Open CommonDialog1.FileName For Input As #1
Do While Not EOF(1)
    For i = 0 To 6
        For j = 0 To 6
        Input #1, Matrix(i, j)
        Next j
    Next i
Loop