题解 | #二叉树的最大深度# 一个更好懂的版本

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param root TreeNode类
     * @return int整型
     */

    private List<Integer> DArr = new ArrayList<Integer>();
    public int maxDepth (TreeNode root) {
        // write code here
        if (root == null) {
            return 0;
        }
        search(root, 1);
        int max = 0;
        for (int i = 0; i < DArr.size(); i++) {
            if (max < DArr.get(i)) {
                max = DArr.get(i);
            }
        }
        return max;
    }

    public int search(TreeNode root, int deepNow) {
	  //左根右
        if (root.left != null) {
            search(root.left, deepNow + 1);
        }
        if (root.left == null && root.right == null) {
            System.out.print(deepNow + "/////");
		  //每个叶子节点的深度都记上
            DArr.add(deepNow);
        }
        if (root.right != null) {
             search(root.right, deepNow + 1);
        }
        return deepNow;
    }
}