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 [4,1] are both considered valid,but the path [1,4,3] 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 [1,3] or [3,1]. 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}; } }
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