Package g1301_1400.s1372_longest_zigzag_path_in_a_binary_tree

Class Solution

  • public class Solution
extends Object
    1372 - Longest ZigZag Path in a Binary Tree.

    Medium

    You are given the root of a binary tree.

    A ZigZag path for a binary tree is defined as follow:

    • Choose any node in the binary tree and a direction (right or left).
    • If the current direction is right, move to the right child of the current node; otherwise, move to the left child.
    • Change the direction from right to left or from left to right.
    • Repeat the second and third steps until you can’t move in the tree.

    Zigzag length is defined as the number of nodes visited - 1. (A single node has a length of 0).

    Return the longest ZigZag path contained in that tree.

    Example 1:

    Input: root = [1,null,1,1,1,null,null,1,1,null,1,null,null,null,1,null,1]

    Output: 3

    Explanation: Longest ZigZag path in blue nodes (right -> left -> right).

    Example 2:

    Input: root = [1,1,1,null,1,null,null,1,1,null,1]

    Output: 4

    Explanation: Longest ZigZag path in blue nodes (left -> right -> left -> right).

    Example 3:

    Input: root = [1]

    Output: 0

    Constraints:

    • The number of nodes in the tree is in the range [1, 5 * 104].
    • 1 <= Node.val <= 100

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • longestZigZag

        public int longestZigZag​(TreeNode root)