我有一个具有以下结构的DataTable：
Root | Level 1 | Level 2 | Level 3 | Tree L | Tree R
Food 1 18
Fruit 2 11
Red 3 6
Cherry 4 5
Yellow 7 10
Banana 8 9
Meat 12 17
Beef 13 14
Pork 15 16
使用C＃，我需要遍历此结构并为每个节点计算正确的Tree L和Tree R值。这只是一个例子，真实结构有几百个节点，至少达到7级，但可能更多。
有人可以建议我如何处理计算左右值的代码吗？
答案 0 :(得分：0)
因此，您希望跟踪树的访问顺序，但您将订单拆分为L和R。这些对应于Visit结构的Node函数的“入口”和“退出”。假设Node类具有Node.Visit()方法，您可以：
private static List<Tuple<char,Node>> VisitOrder = new List<Tuple<char,Node>>();
public void Visit()
{
VisitOrder.Add(Tuple.Create('L', this));
// whatever visit logic you use here
VisitOrder.Add(Tuple.Create('R', this));
}
完成后，您所要做的就是查看VisitOrder值。它们以递增的顺序存储在List中，其中索引对应于它在访问序列中的位置。然后，List中的每个项目都是Tuple，用于说明它对应的值以及访问过的Node。
修改
要获得最终输出格式，您可以执行以下操作：
var LTree = VisitOrder
.Where(t => t.First == 'L')
.Select((t, i) => String.Format("{0}) {1}", i + 1, t.Second.Name));
var RTree = VisitOrder
.Where(t => t.First == 'R')
.Select((t, i) => String.Format("{0}) {1}", i + 1, t.Second.Name));
答案 1 :(得分：0)
以下是我弄清楚的方法：
private class FolderRow
{
public int Indent
{
get { return this.Row.GetValue("Indent", 0); }
set { this.Row["Indent"] = value; }
}
public int Left
{
get { return this.Row.GetValue("Tree L", 0); }
set { this.Row["Tree L"] = value; }
}
public int Right
{
get { return this.Row.GetValue("Tree R", 0); }
set { this.Row["Tree R"] = value; }
}
public Guid Id
{
get { return this.Row.GetValue("FolderID", Guid.Empty); }
}
public DataRow Row { get; private set; }
public int RowNum { get; set; }
public bool RowComplete { get { return this.Left > 0 && this.Right > 0; } }
public FolderRow(DataRow row, int rowNum)
{
this.Row = row;
this.RowNum = rowNum;
}
}
[TestMethod]
public void ImportFolderStructure()
{
var inputTable = FileUtil.GetDataSetFromExcelFile(new FileInfo(@"c:\SampleTree.xlsx")).Tables[0];
var currentLevel = 0;
var nodeCount = 1;
var currentRow = 0;
inputTable.Columns.Add("Indent", typeof (int));
inputTable.Columns.Add("Path", typeof (string));
var rightStack = new List<FolderRow>();
foreach (DataRow row in inputTable.Rows)
row["Indent"] = GetLevelPopulated(row);
foreach (DataRow row in inputTable.Rows)
{
if (row.GetValue("Indent", 0) == 0)
row["Tree L"] = 1;
}
while (true)
{
var row = GetRow(inputTable, currentRow);
if (row.Indent == 0)
{
currentRow++;
rightStack.Add(row);
continue;
}
// if the indent of this row is greater than the previous row ...
if (row.Indent > currentLevel)
{
currentLevel++;
nodeCount++;
row.Left = nodeCount;
// ... check the next row to see if it is further indented
currentRow = HandleNextRow(row, currentRow, rightStack, inputTable, ref currentLevel, ref nodeCount);
} else if (row.Indent == currentLevel)
{
nodeCount++;
row.Left = nodeCount;
currentRow = HandleNextRow(row, currentRow, rightStack, inputTable, ref currentLevel, ref nodeCount);
} else if (row.Indent < currentLevel)
{
currentLevel--;
nodeCount++;
row.Left = nodeCount;
currentRow = HandleNextRow(row, currentRow, rightStack, inputTable, ref currentLevel, ref nodeCount);
}
if (inputTable.Rows.Cast<DataRow>().Select(r => new FolderRow(r, -1)).All(r => r.RowComplete))
break;
}
}
private int HandleNextRow(FolderRow row, int currentRow, List<FolderRow> rightStack, DataTable inputTable, ref int currentLevel,
ref int nodeCount)
{
var nextRow = GetRow(inputTable, currentRow + 1);
if (nextRow != null)
{
if (nextRow.Indent > row.Indent)
{
// ok the current row has a child so we will need to set the tree right of that, add to stack
rightStack.Add(row);
}
else if (nextRow.Indent == row.Indent)
{
nodeCount++;
row.Right = nodeCount;
}
else if (nextRow.Indent < row.Indent)
{
nodeCount++;
row.Right = nodeCount;
nodeCount++;
// here we need to get the most recently added row to rightStack, set the Right to the current nodeCount
var stackLast = rightStack.LastOrDefault();
if (stackLast != null)
{
stackLast.Right = nodeCount;
rightStack.Remove(stackLast);
}
currentLevel--;
}
currentRow++;
if (rightStack.Count > 1)
{
// before we move on to the next row, we need to check if there is more than one row still in right stack and
// the new current row's ident is less than the current branch (not current leaf)
var newCurrentRow = GetRow(inputTable, currentRow);
var stackLast = rightStack.LastOrDefault();
if (newCurrentRow.Indent == stackLast.Indent)
{
nodeCount++;
stackLast.Right = nodeCount;
rightStack.Remove(stackLast);
}
}
}
else
{
// reached the bottom
nodeCount++;
row.Right = nodeCount;
// loop through the remaining items in rightStack and set their right values
var stackLast = rightStack.LastOrDefault();
while (stackLast != null)
{
nodeCount++;
stackLast.Right = nodeCount;
rightStack.Remove(stackLast);
stackLast = rightStack.LastOrDefault();
}
}
return currentRow;
}
private FolderRow GetRow(DataTable inputTable, int rowCount)
{
if (rowCount >= inputTable.Rows.Count)
return null;
return rowCount < 0 ? null : new FolderRow(inputTable.Rows[rowCount],rowCount);
}
private int GetLevelPopulated(DataRow row)
{
var level = 0;
while (level < 14)
{
if (level == 0 && row["Root"] != DBNull.Value)
return level;
level++;
if (row["Level " + level] != DBNull.Value)
return level;
}
return -1;
}