preorder traversal indentation

Author: ivanmmarkovic

Ch06. Trees and Tree Algorithms/tree traversal/preorder-indentation.py

@@ -0,0 +1,48 @@
+from tree import TreeNode
+from stack import Stack
+
+import operator
+
+opers = {'+':operator.add, '-':operator.sub, '*':operator.mul, '/':operator.truediv}
+
+import re
+pattern = re.compile("[0-9]")
+
+string = "( ( 10 + 5 ) * 3 )"
+
+def treeParser(string: str)->TreeNode:
+    string = string.split()
+    tree = TreeNode()
+    stack: Stack = Stack()
+    currentTree: TreeNode = tree
+    stack.push(tree)
+    for item in string:
+        if item == "(":
+            currentTree.insertLeft()
+            stack.push(currentTree)
+            currentTree = currentTree.getLeftChild()
+        elif item == ")":
+            currentTree = stack.pop()
+        elif item in "+-*/":
+            currentTree.setRootValue(item)
+            currentTree.insertRight()
+            stack.push(currentTree)
+            currentTree = currentTree.getRightChild()
+        elif pattern.match(item):
+            currentTree.setRootValue(int(item))
+            currentTree = stack.pop()
+        else:
+            raise ValueError()
+    
+    return tree
+
+tree: TreeNode = treeParser(string)
+
+def prettyPrint(bt: TreeNode, indent: int):
+    print(indent * ".", bt.key)
+    if bt.leftChild is not None:
+        prettyPrint(bt.leftChild, indent + 2)
+    if bt.rightChild is not None:
+        prettyPrint(bt.rightChild, indent + 2)
+
+prettyPrint(bt, 0)