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63 lines
1.5 KiB
63 lines
1.5 KiB
# Various iterative ways of traversing a tree.
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def inorder_traversal(root):
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"""
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:type root: TreeNode
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:rtype: List[int]
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"""
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if not root:
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return []
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result = []
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stack = [root]
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while len(stack) > 0:
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curr_node = stack.pop()
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if curr_node.left:
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stack.append(curr_node)
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stack.append(curr_node.left)
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curr_node.left = None
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else:
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result.append(curr_node.val)
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if curr_node.right:
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stack.append(curr_node.right)
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return result
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def preorder_traversal(root):
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"""
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:type root: TreeNode
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:rtype: List[int]
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"""
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if not root:
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return []
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result = []
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stack = [root]
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while len(stack) > 0:
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curr_node = stack.pop()
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result.append(curr_node.val)
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if curr_node.right:
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stack.append(curr_node.right)
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if curr_node.left:
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stack.append(curr_node.left)
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return result
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def postorder_traversal(root):
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"""
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:type root: TreeNode
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:rtype: List[int]
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"""
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if not root:
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return []
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result = []
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stack = [root]
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while len(stack) > 0:
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curr_node = stack.pop()
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if curr_node.left:
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stack.append(curr_node)
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stack.append(curr_node.left)
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curr_node.left = None
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elif curr_node.right:
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stack.append(curr_node)
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stack.append(curr_node.right)
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curr_node.right = None
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else:
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result.append(curr_node.val)
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return result
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