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https://github.com/TheAlgorithms/Python.git
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107 lines
2.9 KiB
Python
107 lines
2.9 KiB
Python
"""
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This is pure python implementation of tree traversal algorithms
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"""
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import queue
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class TreeNode:
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def __init__(self, data):
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self.data = data
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self.right = None
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self.left = None
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def build_tree():
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print("Enter the value of the root node: ", end="")
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data = eval(input())
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if data < 0:
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return None
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else:
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q = queue.Queue()
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tree_node = TreeNode(data)
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q.put(tree_node)
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while not q.empty():
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node_found = q.get()
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print("Enter the left node of %s: " % node_found.data, end="")
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left_data = eval(input())
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if left_data >= 0:
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left_node = TreeNode(left_data)
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node_found.left = left_node
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q.put(left_node)
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print("Enter the right node of %s: " % node_found.data, end="")
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right_data = eval(input())
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if right_data >= 0:
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right_node = TreeNode(right_data)
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node_found.right = right_node
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q.put(right_node)
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return tree_node
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def pre_order(node):
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if not isinstance(node, TreeNode) or not node:
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print("Invalid input")
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return
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print(node.data, end=" ")
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pre_order(node.left)
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pre_order(node.right)
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def in_order(node):
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if not isinstance(node, TreeNode) or not node:
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return
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in_order(node.left)
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print(node.data, end=" ")
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in_order(node.right)
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def post_order(node):
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if not isinstance(node, TreeNode) or not node:
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return
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post_order(node.left)
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post_order(node.right)
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print(node.data, end=" ")
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def level_order(node):
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if not isinstance(node, TreeNode) or not node:
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return
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q = queue.Queue()
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q.put(node)
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while not q.empty():
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node_dequeued = q.get()
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print(node_dequeued.data, end=" ")
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if node_dequeued.left:
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q.put(node_dequeued.left)
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if node_dequeued.right:
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q.put(node_dequeued.right)
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if __name__ == '__main__':
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import sys
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print("\n********* Binary Tree Traversals ************\n")
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# For python 2.x and 3.x compatibility: 3.x has not raw_input builtin
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# otherwise 2.x's input builtin function is too "smart"
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if sys.version_info.major < 3:
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input_function = raw_input
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else:
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input_function = input
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node = build_tree()
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print("\n********* Pre Order Traversal ************")
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pre_order(node)
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print("\n******************************************\n")
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print("\n********* In Order Traversal ************")
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in_order(node)
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print("\n******************************************\n")
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print("\n********* Post Order Traversal ************")
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post_order(node)
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print("\n******************************************\n")
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print("\n********* Level Order Traversal ************")
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level_order(node)
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print("\n******************************************\n")
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