105-Construct-Binary-Tree-from-Preorder-and-Inorder-Traversal.py

class Solution:
    def buildTree(self, preorder: List[int], inorder: List[int]) -> Optional[TreeNode]:
        inorder_index_mapping = {}
        for k,v in enumerate(inorder):
            inorder_index_mapping[v] = k
        index = 0
        def buildtree(left,right):
            nonlocal index
            if left>right:
                return None
            root_val=preorder[index]
            root = TreeNode(root_val)
            index+=1
            root.left = buildtree(left, inorder_index_mapping[root_val]-1)
            root.right = buildtree(inorder_index_mapping[root_val]+1, right)
            return root
        return buildtree(0, len(preorder)-1)