Boundary of Binary Tree
Role: Software Engineer
Given the root of a binary tree, return the values of its boundary in anti-clockwise direction starting from the root.
The boundary includes:
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The root.
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The left boundary (excluding leaves).
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All leaf nodes from left to right.
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The right boundary in reverse order (excluding leaves).
If the root has no left or right subtree, then the root itself is the boundary.
Examples
Example 1:
Input: root = [1,null,2,3,4]
Output: [1,3,4,2]
Example 2:
Input: root = [1,2,3,4,5,6,null,null,null,7,8,9,10]
Output: [1,2,4,7,8,9,10,6,3]
Constraints
1 <= Number of nodes <= 10^4-1000 <= Node.val <= 1000