g0901_1000.s0971_flip_binary_tree_to_match_preorder_traversal

Class Solution

java.lang.Object

g0901_1000.s0971_flip_binary_tree_to_match_preorder_traversal.Solution

public class Solution
extends Object

971 - Flip Binary Tree To Match Preorder Traversal.

Medium

You are given the root of a binary tree with n nodes, where each node is uniquely assigned a value from 1 to n. You are also given a sequence of n values voyage, which is the desired pre-order traversal of the binary tree.

Any node in the binary tree can be flipped by swapping its left and right subtrees. For example, flipping node 1 will have the following effect:

Flip the smallest number of nodes so that the pre-order traversal of the tree matches voyage.

Return a list of the values of all flipped nodes. You may return the answer in any order. If it is impossible to flip the nodes in the tree to make the pre-order traversal match voyage_, return the list_ [-1].

Example 1:

Input: root = [1,2], voyage = [2,1]

Output: [-1]

Explanation: It is impossible to flip the nodes such that the pre-order traversal matches voyage.

Example 2:

Input: root = [1,2,3], voyage = [1,3,2]

Output: [1]

Explanation: Flipping node 1 swaps nodes 2 and 3, so the pre-order traversal matches voyage.

Example 3:

Input: root = [1,2,3], voyage = [1,2,3]

Output: []

Explanation: The tree’s pre-order traversal already matches voyage, so no nodes need to be flipped.

Constraints:

• The number of nodes in the tree is n.
• n == voyage.length
• 1 <= n <= 100
• 1 <= Node.val, voyage[i] <= n
• All the values in the tree are unique.
• All the values in voyage are unique.

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
List<Integer>	flipMatchVoyage(TreeNode root, int[] voyage)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

flipMatchVoyage

public List<Integer> flipMatchVoyage(TreeNode root,
                                     int[] voyage)