https://leetcode.com/problems/binary-tree-preorder-traversal/ 题意分析: 前序遍历一棵树,递归的方法很简单。那么非递归的方法呢。 题目思路: 前序遍历的顺序是先遍历根节点,再遍历左子树,最后遍历右子树。递归的方法很直观。非递归的方法是利用栈来实现,后进先出,先放右子树进入栈。代码给的是非递归的方法。
代码 python defpreorderTraversal(root):""" :type root: TreeNode :rtype: List[int] """rs=[]defdfs(node):ifnotnode:returnrs.append(node.val)dfs(node.left)dfs(node.right)dfs(root)returnrsdefpreorderTraversalV2(root):defdfs(node):ifnotnode:return[]return[node.val]+dfs(node.left)+dfs...
curr= stack[len(stack) - 1]if(curr.left == Noneandcurr.right == None)or(preand(pre == curr.leftorpre ==curr.right)): list.append(curr.val) stack.pop() pre=currelse:ifcurr.right: stack.append(curr.right)ifcurr.left: stack.append(curr.left)returnlistdefpostorderTraversal(self, roo...
二叉树的遍历 class treeNode: def __init__(self, x): self.val = x self.left = None self.right = None 深度优先搜索(Depth First Search, DFS)非递归的版本在完整代码中前序遍历 PreOrder Traversal:根-左结点-右结点 def preorder(root): if root is None: return [] return...
同Construct Binary Tree from Inorder and Postorder Traversal(Python版) # Definition for a binary tree node. # class TreeNode: # def __init__(self, val=0, left=None, right=None): # self.val = val # self.left = left # self.right = right class Solution: def buildTree(self, pre...
Construct Binary Tree from Preorder and Inorder Traversal LeetCode—105. Construct Binary Tree from Preorder and Inorder Traversal 题目 根据前序遍历和中序遍历建立二叉树。注意二叉树中没有重复的数字。 思路及解法 根据前序遍历和中序遍历的特点,通过前序遍历列表确定根节点,在中序遍历的列表里找出根...
1 InOrder Traversal in Python 0 Python: Build Binary Tree with Pre and Inorder 0 Python Ordered List Preorder Tree Traversal 0 how to iteratively present a preorder (binary tree)? 3 Ouputting the binary tree in using in-order and pre-order traversal 1 Construct Binary tree from ...
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...
Search − Searches an element in a tree. Insert − Inserts an element in a tree. Pre-order Traversal − Traverses a tree in a pre-order manner. In-order Traversal − Traverses a tree in an in-order manner. Post-order Traversal − Traverses a tree in a post-order manner....
1、先序遍历 2、每次记录层次,作为子数组的index 3、将每次的root节点append到指定层次的子数组中 具体代码 # Definition for a binary tree node.# class TreeNode(object):# def __init__(self, x):# self.val = x# self.left = None# self.right = NoneclassSolution(object):deflevelOrder(self,...