Watch 10 video solutions for Construct String from Binary Tree, a medium level problem involving String, Tree, Depth-First Search. This walkthrough by Inside code has 224,586 views views. Want to try solving it yourself? Practice on FleetCode or read the detailed text solution.
Given the root node of a binary tree, your task is to create a string representation of the tree following a specific set of formatting rules. The representation should be based on a preorder traversal of the binary tree and must adhere to the following guidelines:
Node Representation: Each node in the tree should be represented by its integer value.
Parentheses for Children: If a node has at least one child (either left or right), its children should be represented inside parentheses. Specifically:
Omitting Empty Parentheses: Any empty parentheses pairs (i.e., ()) should be omitted from the final string representation of the tree, with one specific exception: when a node has a right child but no left child. In such cases, you must include an empty pair of parentheses to indicate the absence of the left child. This ensures that the one-to-one mapping between the string representation and the original binary tree structure is maintained.
In summary, empty parentheses pairs should be omitted when a node has only a left child or no children. However, when a node has a right child but no left child, an empty pair of parentheses must precede the representation of the right child to reflect the tree's structure accurately.
Example 1:
Input: root = [1,2,3,4] Output: "1(2(4))(3)" Explanation: Originally, it needs to be "1(2(4)())(3()())", but you need to omit all the empty parenthesis pairs. And it will be "1(2(4))(3)".
Example 2:
Input: root = [1,2,3,null,4] Output: "1(2()(4))(3)" Explanation: Almost the same as the first example, except the()after2is necessary to indicate the absence of a left child for2and the presence of a right child.
Constraints:
[1, 104].-1000 <= Node.val <= 1000