549. Binary Tree Longest Consecutive Sequence II

Given a binary tree, you need to find the length of Longest Consecutive Path in Binary Tree.
Especially, this path can be either increasing or decreasing. For example, [1,2,3,4] and [4,3,2,1] are both considered valid, but the path [1,2,4,3] is not valid. On the other hand, the path can be in the child-Parent-child order, where not necessarily be parent-child order.
Example 1:

Input:
        1
       / \
      2   3
Output: 2
Explanation: The longest consecutive path is [1, 2] or [2, 1].

Example 2:

Input:
        2
       / \
      1   3
Output: 3
Explanation: The longest consecutive path is [1, 2, 3] or [3, 2, 1].




https://leetcode.com/problems/binary-tree-longest-consecutive-sequence-ii/solution/




public class Solution {
    int maxval = 0;
    public int longestConsecutive(TreeNode root) {
        longestPath(root);
        return maxval;
    }
    public int[] longestPath(TreeNode root) {
        if (root == null)
            return new int[] {0,0};
        int inr = 1, dcr = 1;
        if (root.left != null) {
            int[] l = longestPath(root.left);
            if (root.val == root.left.val + 1)
                dcr = l[1] + 1;
            else if (root.val == root.left.val - 1)
                inr = l[0] + 1;
        }
        if (root.right != null) {
            int[] r = longestPath(root.right);
            if (root.val == root.right.val + 1)
                dcr = Math.max(dcr, r[1] + 1);
            else if (root.val == root.right.val - 1)
                inr = Math.max(inr, r[0] + 1);
        }
        maxval = Math.max(maxval, dcr + inr - 1);
        return new int[] {inr, dcr};
    }
}