2021.7.5-leetcode104 二叉树的最大深度

二叉树的最大深度 104

解法通102 用广度优先遍历

/**
 * 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 maxDepth(TreeNode root) {
        List<List<Integer>> result = new ArrayList<>();
        if(root == null)
            return result.size();
        Queue<TreeNode> queue = new LinkedList<TreeNode>();
        queue.add(root);
        while(!queue.isEmpty()){
            List<Integer> list = new ArrayList();
            int size = queue.size();
            for(int i = 0;i<size;i++){
                TreeNode currentNode = queue.poll();
                list.add(currentNode.val);
                if(currentNode.left != null)
                    queue.add(currentNode.left);//先把左节点加入队列
                if(currentNode.right != null)
                    queue.add(currentNode.right);
            }
            result.add(list);
        }
        return result.size();
        
    }
   
}