Package g1001_1100.s1028_recover_a_tree_from_preorder_traversal

Class Solution

  • public class Solution
extends Object
    1028 - Recover a Tree From Preorder Traversal.

    Hard

    We run a preorder depth-first search (DFS) on the root of a binary tree.

    At each node in this traversal, we output D dashes (where D is the depth of this node), then we output the value of this node. If the depth of a node is D, the depth of its immediate child is D + 1. The depth of the root node is 0.

    If a node has only one child, that child is guaranteed to be the left child.

    Given the output traversal of this traversal, recover the tree and return its root.

    Example 1:

    Input: traversal = “1-2–3–4-5–6–7”

    Output: [1,2,5,3,4,6,7]

    Example 2:

    Input: traversal = “1-2–3—4-5–6—7”

    Output: [1,2,5,3,null,6,null,4,null,7]

    Example 3:

    Input: traversal = “1-401–349—90–88”

    Output: [1,401,null,349,88,90]

    Constraints:

    • The number of nodes in the original tree is in the range [1, 1000].
    • 1 <= Node.val <= 109

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • recoverFromPreorder

        public TreeNode recoverFromPreorder​(String traversal)