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Update bt_construct_inorder_preorder.py

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bt3gl 2023-08-08 19:56:03 -07:00 committed by GitHub
parent 14404c47c8
commit fcd4eb423b
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1 changed files with 5 additions and 4 deletions
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trees/bt_construct_inorder_preorder.py
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@ -3,15 +3,16 @@
# author: bt3gl
def build_tree(preorder, inorder) -> Optional[Node]:
def build_tree(preorder, inorder):
def helper(left, right, index_map):
if left > right:
return None
root = Node(preorder.pop(0)) # # this order change from postorder
index_here = index_map[root.val]
node = preorder.pop(0) # this order change from postorder
root = Node(node.val)
index_here = index_map[node.val]
root.left = helper(left, index_here - 1, index_map) # this order change from postorder
root.right = helper(index_here + 1, right, index_map)