0623. Add One Row to Tree

623. Add One Row to Tree

Topics

• Binary Tree
• Tree
• Breadth-first Search
• Depth-first Search

Given the root of a binary tree and two integers val and depth, add a row of nodes with value val at the given depth depth.

Note that the root node is at depth 1.

The adding rule is:

• Given the integer depth, for each not null tree node cur at the depth depth - 1, create two tree nodes with value val as cur's left subtree root and right subtree root.
• cur's original left subtree should be the left subtree of the new left subtree root.
• cur's original right subtree should be the right subtree of the new right subtree root.
• If depth == 1 that means there is no depth depth - 1 at all, then create a tree node with value val as the new root of the whole original tree, and the original tree is the new root's left subtree.  

Example 1:

Input: root = [4,2,6,3,1,5], val = 1, depth = 2
Output: [4,1,1,2,null,null,6,3,1,5]

Example 2:

Input: root = [4,2,null,3,1], val = 1, depth = 3
Output: [4,2,null,1,1,3,null,null,1]

 

Constraints:

• The number of nodes in the tree is in the range [1, 10^4].
• The depth of the tree is in the range [1, 10^4].
• -100 <= Node.val <= 100
• -10^5 <= val <= 10^5
• 1 <= depth <= the depth of tree + 1