力扣hot100 - 二叉树的直径

题目思路经过某一个节点的最大长度为 左子树高度 右子树高度。我们从下往上遍历计算左子树和右子树的高度在这个过程中不断更新最大长度。/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode() {} * TreeNode(int val) { this.val val; } * TreeNode(int val, TreeNode left, TreeNode right) { * this.val val; * this.left left; * this.right right; * } * } */ class Solution { public int maxlength 0; public int diameterOfBinaryTree(TreeNode root) { dfs(root); return maxlength; } public int dfs(TreeNode root){ if(root null) return 0; int l dfs(root.left); int r dfs(root.right); maxlength Math.max(l r , maxlength); return Math.max(l , r) 1; } }