backtrack

1、46题，全排列 https://leetcode-cn.com/problems/permutations/ class Solution(object): def permute(self, nums): """ :type nums: List[int] :rtype: List[List[int]] """ n = len(nums) results = [] def backtrack(first = 0): if first == n: results.append(nums[:]) return for i in range(first, n): nums[first], nums[i] = nums[i], nums[first] backtrack(first + 1) nums[first], nums[i] = nums[i], nums[first] backtrack() return results 2、47题，全排列二 https://leetcode-cn.com/problems/permutations-ii/ class Solution(object): def permuteUnique(self, nums): """ :type nums: List[int] :rtype: List[List[int]] """ n = len

官网为 www.arachni-scanner.com ，有一些说明，以下为本人安装的操作记录： 使用Gem下载: $ gem install arachni 出错： ERROR: Error installing arachni: dm-core requires addressable (~> 2.2.4, runtime) 应该是依赖性问题。 查一下本地gems： $ gem list --local|grep dm-core 的确没有dm-core 查一下addressable： $gem list --local|grep addressable addressable (2.3.2) 我有些明白了，本地addressable是2.3.2的，而安装arachni需要dm-core，本地没有所以要下载，而dm-core依赖的addressable是2.2.4，所以这个依赖性要手工解决，即将我们系统中已安装的addressable旧版本：-（我觉得应该不是新版本不兼容旧版本的问题，没学过ruby，也不大懂）～～ 安装dm-core： $ gem install dm-core Successfully installed addressable-2.2.8 Successfully installed dm-core-1.2.0 2 gems installed

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I need to match certain URLs in web application, i.e. /123,456,789 , and wrote this regex to match the pattern: r'(\d+(,)?)+/$' I noticed that it does not seem to evaluate, even after several minutes when testing the pattern: re.findall(r'(\d+(,)?)+/$', '12345121,223456,123123,3234,4523,523523') The expected result would be that there were no matches. This expression, however, executes almost immediately (note the trailing slash): re.findall(r'(\d+(,)?)+/$', '12345121,223456,123123,3234,4523,523523/') Is this a bug? 回答1: There is some

2019独角兽企业重金招聘Python工程师标准>>> 问题描述： 　　有一批共n个集装箱要装上2艘载重量分别为c1和c2的轮船，其中集装箱i的重量是wi，且不能超。 算法思想： 　　最优装载方案： 将第一艘轮船尽可能的装满；　　然后将剩余的装载第二艘船上 算法描述： template < class Type > class Loading { friend Type MaxLoading ( Type [], Type , int ); private : void Backtrack ( int i ); int n ; Type * w , c , cw , bestw ; }; template < class Type > void Loading < Type >:: Backtrack ( int i ) { if ( i > n ) { if ( cw > bestw ) bestw = cw ; return ; } if ( cw + w [ i ] <= c ) { cw += w [ i ]; Backtrack ( i + 1 ); cw -= w [ i ]; } Backtrack ( i + 1 ); } template < class Type > Type MaxLoading ( Type w [], Type c , int n ) {