题解 | #统计农场牛数量#
统计农场牛数量
https://www.nowcoder.com/practice/c18924a6debf437180d77baec91dc586
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 */ public int countNodes (TreeNode root) { // write code here List<Integer> list = new ArrayList<>(); preOrder(root,list); return list.size(); } public void preOrder(TreeNode node,List<Integer> list){ if(node == null){ return; } list.add(node.val); preOrder(node.left,list); preOrder(node.right,list); } }