LeetCode刷题实战549：二叉树中最长的连续序列
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.
解题
https://blog.csdn.net/qq_29051413/article/details/108559688
思路：
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};
}
}