1vector<int> preorderTraversal(TreeNode*root) {2vector<int>rVec;3stack<TreeNode *>st;4TreeNode *tree =root;5while(tree || !st.empty())6{7if(tree)8{9st.push(tree);10rVec.push_back(tree->val);11tree = tree->left;12}13else14{15tree =st.top();16st.pop();17tree = tree-...
root.left.right =newTreeNode(3); root.right =newTreeNode(6); root.right.left =newTreeNode(5); root.right.right =newTreeNode(7); root.right.right.right =newTreeNode(8); System.out.println(Main28.preorderTraversal(root)); } publicstaticclassTreeNode { intval; TreeNode left; TreeNode...
public List<Integer> preorderTraversal(TreeNode root) { List<Integer> list = new ArrayList<>(); preorderTraversalHelper(root, list); return list; } private void preorderTraversalHelper(TreeNode root, List<Integer> list) { if (root == null) { return; } list.add(root.val); preorderTrav...
输入:[1,null,2,3] 输出:[1,2,3] 进阶:递归算法很简单,你可以通过迭代算法完成吗? 解题思路 用栈(Stack)的思路来处理问题。 前序遍历的顺序为根-左-右,具体算法为: 把根节点push到栈中 循环检测栈是否为空,若不空,则取出栈顶元素,保存其值 看其右子节点是否存在,若存在则push到栈中 看其左子节点,...
144. Binary Tree Preorder Traversal刷题笔记 问题描述前序遍历。注意嵌套函数里的list应该用append而不是+=来添加元素 # Definition for a binary tree node. # class TreeNode: # def __init__(self, val=0, left=None, right=None): # self.val = val...
binary-tree-preorder-traversal二叉树的前序遍历,代码:packagecom.niuke.p7;importjava.util.ArrayList;importjava.util.Stack;publicclassSolution{publicArrayList<Integer>preorderTraversal(Tre
Leetcode 144 binary tree preorder traversal 下面这种写法使用了一个辅助结点p,这种写法其实可以看作是一个模版,对应的还有中序和后序的模版写法,形式很统一,方便于记忆。 辅助结点p初始化为根结点,while循环的条件是栈不为空或者辅助结点p不为空,在循环中首先判断如果辅助结点p存在,那么先将p加入栈中,然后将...
每天一算:Binary Tree Preorder Traversal 程序员吴师兄 + 关注 预计阅读时间2分钟 6 年前 LeetCode上第144 号问题:二叉树的前序遍历 题目 给定一个二叉树,返回它的 前序 遍历。 示例: 输入: [1,null,2,3] 输出: [1,2,3] 进阶: 递归算法很简单,你可以通过迭代算法完成吗? 解题思路 用栈(Stack)...
Unfortunately, the .NET Framework does not contain a binary tree class, so in order to better understand binary trees, let's take a moment to create our own binary tree class. The First Step: Creating a Base Node Class The first step in designing our binary tree class is to create a ...
Unfortunately, the .NET Framework does not contain a binary tree class, so in order to better understand binary trees, let's take a moment to create our own binary tree class. The First Step: Creating a Base Node Class The first step in designing our binary tree class is to create a ...