Leetcode Problem 1932. Merge BSTs to Create Single BST

1932. Merge BSTs to Create Single BST

Leetcode Solutions

In-order Traversal and Node Merging

  1. Create a map (nodes) to store the value-to-node relationship for all nodes in the input list of trees.
  2. Create a map (indeg) to count the incoming edges for each node value.
  3. Identify the root node for the BST, which should have no incoming edges (indeg = 0). If there is not exactly one such node, return None.
  4. Perform an in-order traversal starting from the root node, updating the current value (self.cur) to ensure the values are strictly increasing.
  5. During traversal, check for cycles by keeping track of seen nodes. If a cycle is detected, mark the tree as invalid.
  6. After traversal, check if all nodes were seen and the traversal was valid. If not, return None.
  7. If the traversal was successful and valid, return the root node of the merged BST.
UML Thumbnail

Building BST by Merging Leaves

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