Fix typo in traversals

traversals/binary_tree_traversals.py

@@ -0,0 +1,109 @@
+"""
+This is pure python implementation of tree traversal algorithms
+"""
+from __future__ import print_function
+import queue
+
+
+class TreeNode:
+    def __init__(self, data):
+        self.data = data
+        self.right = None
+        self.left = None
+
+
+def build_tree():
+    print("\n********Press N to stop entering at any point of time********\n")
+    print("Enter the value of the root node: ", end="")
+    check=input()
+    if check=='N' or check=='n':
+        return None 
+    data=int(check)
+    q = queue.Queue()
+    tree_node = TreeNode(data)
+    q.put(tree_node)
+    while not q.empty():
+        node_found = q.get()
+        print("Enter the left node of %s: " % node_found.data, end="")
+        check=input()
+        if check=='N' or check =='n':
+            return tree_node
+        left_data = int(check)
+        left_node = TreeNode(left_data)
+        node_found.left = left_node
+        q.put(left_node)
+        print("Enter the right node of %s: " % node_found.data, end="")
+        check = input()
+        if check == 'N' or check == 'n':
+            return tree_node
+        right_data = int(check)
+        right_node = TreeNode(right_data)
+        node_found.right = right_node
+        q.put(right_node)
+
+
+def pre_order(node):
+    if not isinstance(node, TreeNode) or not node:
+        return
+    print(node.data, end=" ")
+    pre_order(node.left)
+    pre_order(node.right)
+
+
+def in_order(node):
+    if not isinstance(node, TreeNode) or not node:
+        return
+    in_order(node.left)
+    print(node.data, end=" ")
+    in_order(node.right)
+
+
+def post_order(node):
+    if not isinstance(node, TreeNode) or not node:
+        return
+    post_order(node.left)
+    post_order(node.right)
+    print(node.data, end=" ")
+
+
+def level_order(node):
+    if not isinstance(node, TreeNode) or not node:
+        return
+    q = queue.Queue()
+    q.put(node)
+    while not q.empty():
+        node_dequeued = q.get()
+        print(node_dequeued.data, end=" ")
+        if node_dequeued.left:
+            q.put(node_dequeued.left)
+        if node_dequeued.right:
+            q.put(node_dequeued.right)
+
+
+if __name__ == '__main__':
+    import sys
+
+    print("\n********* Binary Tree Traversals ************\n")
+    # For python 2.x and 3.x compatibility: 3.x has no raw_input builtin
+    # otherwise 2.x's input builtin function is too "smart"
+    if sys.version_info.major < 3:
+        input_function = raw_input
+    else:
+        input_function = input
+
+    node = build_tree()
+    print("\n********* Pre Order Traversal ************")
+    pre_order(node)
+    print("\n******************************************\n")
+
+    print("\n********* In Order Traversal ************")
+    in_order(node)
+    print("\n******************************************\n")
+
+    print("\n********* Post Order Traversal ************")
+    post_order(node)
+    print("\n******************************************\n")
+
+    print("\n********* Level Order Traversal ************")
+    level_order(node)
+    print("\n******************************************\n")