Adding function for actual level order traversal (#699)

traversals/binary_tree_traversals.py

@@ -2,6 +2,7 @@
 This is pure python implementation of tree traversal algorithms
 """
 from __future__ import print_function
+
 import queue
 
 try:
@@ -46,6 +47,7 @@ def build_tree():
         node_found.right = right_node
         q.put(right_node)
 
+
 def pre_order(node):
     if not isinstance(node, TreeNode) or not node:
         return
@@ -53,6 +55,7 @@ def pre_order(node):
     pre_order(node.left)
     pre_order(node.right)
 
+
 def in_order(node):
     if not isinstance(node, TreeNode) or not node:
         return
@@ -82,6 +85,26 @@ def level_order(node):
         if node_dequeued.right:
             q.put(node_dequeued.right)
 
+
+def level_order_actual(node):
+    if not isinstance(node, TreeNode) or not node:
+        return
+    q = queue.Queue()
+    q.put(node)
+    while not q.empty():
+        list = []
+        while not q.empty():
+            node_dequeued = q.get()
+            print(node_dequeued.data, end=" ")
+            if node_dequeued.left:
+                list.append(node_dequeued.left)
+            if node_dequeued.right:
+                list.append(node_dequeued.right)
+        print()
+        for node in list:
+            q.put(node)
+
+
 # iteration version
 def pre_order_iter(node):
     if not isinstance(node, TreeNode) or not node:
@@ -98,6 +121,7 @@ def pre_order_iter(node):
         # start to traverse its right child
         n = n.right
 
+
 def in_order_iter(node):
     if not isinstance(node, TreeNode) or not node:
         return
@@ -111,6 +135,7 @@ def in_order_iter(node):
         print(n.data, end=" ")
         n = n.right
 
+
 def post_order_iter(node):
     if not isinstance(node, TreeNode) or not node:
         return
@@ -127,6 +152,7 @@ def post_order_iter(node):
     while stack2:  # pop up from stack2 will be the post order
         print(stack2.pop().data, end=" ")
 
+
 if __name__ == '__main__':
     print("\n********* Binary Tree Traversals ************\n")
 
@@ -147,6 +173,10 @@ if __name__ == '__main__':
     level_order(node)
     print("\n******************************************\n")
 
+    print("\n********* Actual Level Order Traversal ************")
+    level_order_actual(node)
+    print("\n******************************************\n")
+
     print("\n********* Pre Order Traversal - Iteration Version ************")
     pre_order_iter(node)
     print("\n******************************************\n")