Log4j由三个重要的组件构成:日志信息的优先级,日志信息的输出目的地,日志信息的输出格式. 日志信息的常用的优先级从高到低有ERROR.WARN. INFO.DEBUG,分别用来指定这条日志信息的重要程度: 日志信息的输出目的地指定了日志将打印到控制台还是文件中: 而输出格式则控制了日志信息的显 示内容. 一.定义配置文件 其实您也可以完全不使用配置文件,而是在代码中配置Log4j环境.但是,使用配置文件将使您的应用程序更加灵活.Log4j支持两种配置文件格式,一种是XML格式的文件,一种是J…

题目链接:Sudoku Solver | LeetCode OJ Write a program to solve a Sudoku puzzle by filling the empty cells. Empty cells are indicated by the character '.'. You may assume that there will be only one unique solution. A sudoku puzzle... ...and its solution n…

题目链接:Valid Sudoku | LeetCode OJ Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. The Sudoku board could be partially filled, where empty cells are filled with the character '.'. A partially filled sudoku which is valid. Note:…

1.文件目录操作命令 (1) ls   显示文件和目录列表 a ls -l  显示文件的详细信息 b ls -a 列出当前目录的所有文件,包含隐藏文件. c stat '目录/文件'   显示指定目录/文件的相关信息,比ls命令显示的内容更多 (2) mkdir '目录'    创建目录 (3) touch '文件名'    当前目录下创建一个空文件 (4) echo '内容'>'文件名'   当前目录下生成一个带内容的文件 (5) cat.tac '文件名'    查看文件中的文本内容 a m…

题目链接:Path Sum II | LeetCode OJ Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example: Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \ 7 2 5 1 return [ [5,4,11,2],…

题目链接:Path Sum | LeetCode OJ Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example: Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11…

题目链接:Balanced Binary Tree | LeetCode OJ Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more tha…

题目链接:Same Tree | LeetCode OJ Given two binary trees, write a function to check if they are equal or not. Two binary trees are considered equal if they are structurally identical and the nodes have the same value. Tags: Depth-first Search 分析 很基本的一道深度优…

题目链接:Recover Binary Search Tree | LeetCode OJ Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. Note: A solution using O(n) space is pretty straight forward. Could you devise a constan…

题目链接:Validate Binary Search Tree | LeetCode OJ Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys less than the node's key. The right…