Leetcode Problem 889. Construct Binary Tree from Preorder and Postorder Traversal

889. Construct Binary Tree from Preorder and Postorder Traversal

Leetcode Solutions

Recursive Tree Construction from Preorder and Postorder Traversals

  1. Start with the full preorder and postorder arrays.
  2. If either array is empty, return None as there are no more nodes to construct.
  3. Create a new tree node with the first value of the preorder array as the root.
  4. If the preorder array has only one element, return the created node as it is a leaf node.
  5. Find the index of the second element of the preorder array in the postorder array. This index will help to determine the size of the left subtree.
  6. Recursively construct the left subtree using the next portion of the preorder array and the corresponding portion of the postorder array.
  7. Recursively construct the right subtree using the remaining elements of the preorder array and the corresponding portion of the postorder array, excluding the last element which is the root.
  8. Assign the constructed left and right subtrees to the root node.
  9. Return the root node.
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Iterative Tree Construction from Preorder and Postorder Traversals

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