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30 lines
887 B
Python
30 lines
887 B
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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# author: bt3gl
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# Given two integer arrays inorder and postorder where inorder is the inorder
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# traversal of a binary tree and postorder is the postorder traversal of the
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# same tree, construct and return the binary tree.
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def fill_tree(i_left, i_right, inorder_map):
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if i_left > i_right:
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return None
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val = postorder.pop()
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root = TreeNode(val)
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index_here = inorder_map[val]
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root.right = fill_tree(index_here + 1, i_right, inorder_map)
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root.left = fill_tree(i_left, index_here - 1, inorder_map)
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return root
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def build_tree(inorder: list[int], postorder: list[int]) -> Optional[TreeNode]:
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inorder_map = {val: index for index, val in enumerate(inorder)}
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return fill_tree(0, len(inorder) - 1, inorder_map)
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