递归（VBA实现）

Posted 2020-11-16 hqczsh

案列： 给定n个数，取任意g个数之和等于h的组合。

采用递归的方式实现：

Option Explicit
Dim arr1(1 To 10000, 1 To 1) As String
Dim k, g, h As Integer
Dim arr
Dim k1

Sub merge()
    k = 0
    Dim t
    t = Timer
    Erase arr1    ‘ 清空数组中数据
    arr = Range("a2:a" & Range("a65535").End(xlUp).Row)
    g = [b2]  ‘个数
    h = [c2]  ‘和
    zuhe 1, 0, "", 0
    Range("d2").Resize(k) = arr1
    [e1] = k1
    MsgBox "找到" & k & "个解！花费" & Format(Timer - t, "0.00") & "秒"

End Sub
Sub zuhe(x%, z%, sr$, gg As Byte)
    If z + arr(x, 1) = h And gg = g - 1 Then
        k = k + 1
        arr1(k, 1) = sr & arr(x, 1) & " = " & h
        Exit Sub
    End If
    If x < UBound(arr) And z < h Then
        If z + arr(x, 1) < h Then
            zuhe x + 1, z + arr(x, 1), sr & arr(x, 1) & "+", gg + 1
        End If
        zuhe x + 1, z, sr, gg
    End If
End Sub

　　递归依次取数，满足x < UBound(arr)，And z < h,执行语句

zuhe x + 1, z + arr(x, 1), sr & arr(x, 1) & "+", gg + 1  ‘取出 

zuhe x + 1, z, sr, gg   ‘释放

arr1(k, 1) = sr & arr(x, 1) & " = " & h     ‘生成的符合条件的组合存在arr1中，　

过程：

 

 遍历（不断的取值和释放值）后得到符合条件的组合。