Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example, [1,1,2] have the following unique permutations: [[1,1,2],[1,2,1],[2,1,1]] 分析
LeetCode刷题笔记第144题:二叉树的前序遍历 题目: 给你二叉树的根节点root ,返回它节点值的前序遍历。 想法: 前序遍历是通过根左右的方式遍历整个树,通过递归的方式遍历树 # Definition for a binary tree node.# class TreeNode:# def __init__(self, val=0, left=None, righ
前序遍历_迭代法 public List<Integer> preorderTraversal(TreeNode root){List<Integer> result = new ArrayList<>();if(root == null) return result;Deque<TreeNode> stack = new ArrayDeque();stack.push(root);while(