题解 | #二叉树的前序遍历#
二叉树的前序遍历
https://www.nowcoder.com/practice/5e2135f4d2b14eb8a5b06fab4c938635
import java.lang.Integer; 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整型一维数组 */ public int[] preorderTraversal (TreeNode root) { // write code here List<Integer> list = new ArrayList<>(); LinkedList<TreeNode> stack = new LinkedList<>(); while(root!=null||!stack.isEmpty()){ while(root!=null){ list.add(root.val); stack.add(root); root = root.left; } root = stack.removeLast().right; } int n = list.size(); int[] res = new int[n]; for(int i = 0; i < n; i++){ res[i] = list.get(i); } return res; } }