Fix positon calculation in TreeDrawer, remove null node's branch display

Author: tautcony

DataStructures/Trees/TreeDrawer.cs

@@ -30,11 +30,11 @@ public static string DrawTree<TKey, TValue>(this IBinarySearchTree<TKey, TValue>
         /// <summary>
         /// /// Recusively draws the tree starting from node.
         /// To construct a full tree representation concatenate the returned list of strings by '\n'.
-        /// 
+        ///
         /// Example:
         /// int position, width;
         /// var fullTree = String.Join("\n", _recursivelyDrawTree(this.Root, out position, out width));
-        /// 
+        ///
         /// Algorithm developed by MIT OCW.
         /// http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-006-introduction-to-algorithms-fall-2011/readings/binary-search-trees/bstsize_r.py
         /// </summary>
@@ -43,43 +43,35 @@ public static string DrawTree<TKey, TValue>(this IBinarySearchTree<TKey, TValue>
         /// <param name="widthOutput"></param>
         /// <returns>List of tree levels as strings.</returns>
         private static List<string> _recursivelyDrawTree<T>
-            (BSTNode<T> node, out int positionOutput, out int widthOutput) 
+            (BSTNode<T> node, out int positionOutput, out int widthOutput)
             where T : IComparable<T>
         {
             widthOutput = 0;
             positionOutput = 0;
-            List<string> listOfLines = new List<string>();
 
             if (node == null)
             {
-                return listOfLines;
+                return new List<string>();
             }
 
             //
             // Variables
-            string nodeLabel;
-
-            List<string> leftLines, rightLines;
-            leftLines = rightLines = new List<string>();
-
-            int leftPosition = 0, rightPosition = 0;
-            int leftWidth = 0, rightWidth = 0;
-            int middle, position_out, width_out;
+            int leftPosition, rightPosition, leftWidth, rightWidth;
 
             //
             // Start drawing
-            nodeLabel = Convert.ToString(node.Value);
+            var nodeLabel = Convert.ToString(node.Value);
 
             // Visit the left child
-            leftLines = _recursivelyDrawTree(node.LeftChild, out leftPosition, out leftWidth);
+            List<string> leftLines = _recursivelyDrawTree(node.LeftChild, out leftPosition, out leftWidth);
 
             // Visit the right child
-            rightLines = _recursivelyDrawTree(node.RightChild, out rightPosition, out rightWidth);
+            List<string> rightLines = _recursivelyDrawTree(node.RightChild, out rightPosition, out rightWidth);
 
             // Calculate pads
-            middle = Math.Max(Math.Max(2, nodeLabel.Length), (rightPosition + leftWidth - leftPosition + 1));
-            position_out = leftPosition + middle;
-            width_out = leftPosition + middle + rightWidth - rightPosition;
+            int middle = Math.Max(Math.Max(2, nodeLabel.Length), (rightPosition + leftWidth - leftPosition + 1));
+            int position_out = leftPosition + middle / 2;
+            int width_out = leftPosition + middle + rightWidth - rightPosition;
 
             while (leftLines.Count < rightLines.Count)
                 leftLines.Add(new String(' ', leftWidth));
@@ -105,23 +97,22 @@ private static List<string> _recursivelyDrawTree<T>
 
             //
             // Construct the list of lines.
-            listOfLines = new List<string>()
+            string leftBranch = node.HasLeftChild ? "/" : " ";
+            string rightBranch = node.HasRightChild ? "\\" : " ";
+
+            List<string> listOfLines = new List<string>()
             {
                 // 0
                 (new String(' ', leftPosition )) + nodeLabel + (new String(' ', (rightWidth - rightPosition))),
 
                 // 1
-                (new String(' ', leftPosition)) + "/" + (new String(' ', (middle - 2))) + "\\" + (new String(' ', (rightWidth - rightPosition))) 
+                (new String(' ', leftPosition)) + leftBranch + (new String(' ', (middle - 2))) + rightBranch + (new String(' ', (rightWidth - rightPosition)))
             };
 
             //
             // Add the right lines and left lines to the final list of lines.
-            listOfLines =
-                listOfLines.Concat(
-                    leftLines.Zip(
-                        rightLines, (left_line, right_line) =>
-                            left_line + (new String(' ', (width_out - leftWidth - rightWidth))) + right_line)
-                ).ToList();
+            listOfLines.AddRange(leftLines.Zip(rightLines, (leftLine, rightLine) =>
+                            leftLine + (new String(' ', (width_out - leftWidth - rightWidth))) + rightLine));
 
             //
             // Return
@@ -210,7 +201,7 @@ private static List<string> _recursivelyDrawTree<TKey, TValue>
                     (new String(' ', leftPosition )) + nodeLabel + (new String(' ', (rightWidth - rightPosition))),
 
                     // 1
-                    (new String(' ', leftPosition)) + "/" + (new String(' ', (middle - padValue))) + "\\" + (new String(' ', (rightWidth - rightPosition))) 
+                    (new String(' ', leftPosition)) + "/" + (new String(' ', (middle - padValue))) + "\\" + (new String(' ', (rightWidth - rightPosition)))
                 };
 
             //