题解 | #牛群的树形结构展开II#
牛群的树形结构展开II
https://www.nowcoder.com/practice/3e89ca58f76d4e6aa44cf29569017410
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 * 中序- 左根右,按照中序遍历,新建节点展开,返回新建节点的头节点 * * @param root TreeNode类 * @return TreeNode类 */ public TreeNode flattenII (TreeNode root) { TreeNode res = new TreeNode(-1); TreeNode index = res; Stack<TreeNode> stack = new Stack<>(); while (!stack.isEmpty() || root != null) { if (root != null) { stack.push(root); root = root.left; } else { TreeNode temp = stack.pop(); index.right = new TreeNode(temp.val); index = index.right; root = temp.right; } } return res.right; } }