104. 二叉树的最大深度

题目描述

方法一：DFS 递归

class Solution {
    public int maxDepth(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int left = maxDepth(root.left);
        int right = maxDepth(root.right);
        return Math.max(left, right) + 1;
    }
}

方法二：BFS

class Solution {
    public int maxDepth(TreeNode root) {
        if(root == null) return 0;
        LinkedList<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        int count = 0;
        while (!queue.isEmpty()) {
            int size = queue.size();
            for (int i = 0; i < size; i++) {
                TreeNode node = queue.removeFirst();
                if (node.left != null) {
                    queue.add(node.left);
                }
                if (node.right != null) {
                    queue.add(node.right);
                }
            }
            count++;
        }
        return count;

    }
}