摘要：Clone an undirected graph. Each node in the graph contains alabeland a list of itsneighbors.OJ's undirected graph serialization:Nodes are labeled uniquely.We use#as a separator for each node, and,as a separator for node label and each neighbor of the node.As an example, consider the serialized g 阅读全文

摘要：Given a binary tree, return thebottom-up level ordertraversal of its nodes' values. (ie, from left to right, level by level from leaf to root).For example:Given binary tree{3,9,20,#,#,15,7}, 3 / \ 9 20 / \ 15 7return its bottom-up level order traversal as:[ [15,7] [9,20], [3],] 解题思... 阅读全文

摘要：Given a 2D board containing'X'and'O', capture all regions surrounded by'X'.A region is captured by flipping all'O's into'X's in that surrounded region .For example,X X X XX O O XX X O XX O X XAfter running your function, the board should be:X X X XX X X XX X X 阅读全文

摘要：[解题思路]记录下一层元素个数，这样每次遍历时就知道何时结束，只需一个queue用一个count来计数每一层的node的个数，/** * Definition for binary tree * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */public class Solution { public ArrayList> levelOrder(TreeNode root) { ... 阅读全文

摘要：[解题思路]二叉树的层序遍历通过使用queue来实现，上网搜索了下，发现该题可以使用栈来解决，通过分析执行结果确实是后进先出这里通过定义leftToRight来表示是从左到右还是从右到左从左到右：先加left后加right从右到左：先加right后加leftorderlevel traversal 遍历最后每行添加到result前 判断是leftToRight 还是Right to Left/** * Definition for binary tree * public class TreeNode { * int val; * TreeNode left; * Tr... 阅读全文

摘要：Given two words (startandend), and a dictionary, find the length of shortest transformation sequence fromstarttoend, such that:Only one letter can be ... 阅读全文