组合总和IV

Sub combinationSum()
    ar = Array(1, 2, 3)
    target = 4
    Dim dp()
    ReDim dp(target + 1)
    dp(0) = 1
    For i = 0 To target
        For j = 0 To UBound(ar)
            If i >= ar(j) Then
                dp(i) = dp(i) + dp(i - ar(j))
            End If
        Next
    Next
    res = dp(target)
End Sub