通过VBA编程，给定一个断面的起点距高程数据分别放在A/B列，输入一个水位C1，计算该水位下的断面平均水深D1

在VBA编程中，你可以使用数组和循环结构来解决这个问题。假设你的数据从A2到B最后一行都有，水位在C1单元格，步骤如下：

1. 定义变量和范围：
- `startDistances` 可能存储在A列，范围是从A2到A(n)，其中n是你数据的最后一个单元格
- `heights` 存储在B列，范围是从B2到B(n)
- `waterLevel` 在C1

2. 创建数组并初始化：

   Dim startDistances() As Double
   ReDim startDistances(1 To n) ' 假设n为A列的最后一行
   For i = 1 To n
       startDistances(i) = Cells(i, 1).Value
   Next i
   
   Dim heightsArray() As Double
   ReDim heightsArray(1 To n)
   For i = 1 To n
       heightsArray(i) = Cells(i, 2).Value
   Next i

3. 计算累计高程：

   Dim cumulatedHeights() As Double
   ReDim cumulatedHeights(1 To n)
   cumulatedHeights(1) = heightsArray(1)
   For i = 2 To n
       cumulatedHeights(i) = cumulatedHeights(i - 1) + heightsArray(i)
   Next i

4. 找到水位对应的位置：

   Dim waterDepthIndex As Long
   waterDepthIndex = ArraySearch(cumulatedHeights, waterLevel, 1, n) ' 搜索函数，返回位置

5. 计算平均水深：

   If waterDepthIndex <> 0 Then
       Dim averageDepth As Double
       averageDepth = (cumulatedHeights(waterDepthIndex) - cumulatedHeights(waterDepthIndex - 1)) / 2 ' 如果找到水位，计算平均深度
       Cells(Cells.Count, 1).Offset(0, 1) = averageDepth ' 将结果放入D1
   Else
       MsgBox "水位不在数据范围内"
   End If

6. 函数示例（用于搜索水位对应的累计高度值）：

   Function ArraySearch(arr(), target As Variant, low As Long, high As Long) As Long
        If high < low Then
            ArraySearch = -1
        ElseIf low = high Then
            If arr(low) = target Then
                ArraySearch = low
            Else
                ArraySearch = -1
            End If
        Else
            midPoint = Int((low + high) / 2)
            If arr(midPoint) >= target Then
                ArraySearch = ArraySearch(arr, target, low, midPoint - 1)
            Else
                ArraySearch = ArraySearch(arr, target, midPoint + 1, high)
            End If
        End If
    End Function