Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail From: Mark Lawrence Newsgroups: comp.lang.python Subject: Re: Find the number of robots needed to walk through the rectangular grid Date: Sat, 9 Apr 2016 20:23:28 +0100 Lines: 39 Message-ID: References: <8c570da8-ab31-44f3-9fdf-83e28741ffe4@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Trace: news.uni-berlin.de HufE4TZwYL8aSbGM2PcZZwi5CoIzWUlxDvfzJerDUBNg== Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.005 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'from:addr:yahoo.co.uk': 0.05; 'column': 0.07; 'subject:number': 0.07; 'grid': 0.09; 'integers': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'successive': 0.09; 'index': 0.13; 'subject: \n ': 0.15; '18:13,': 0.16; '2016': 0.16; 'arbitrarily': 0.16; 'horizontally': 0.16; 'movements,': 0.16; 'nodes': 0.16; 'queue?': 0.16; 'received:80.91.229.3': 0.16; 'received:io': 0.16; 'received:plane.gmane.org': 0.16; 'received:psf.io': 0.16; 'row': 0.16; 'structure.': 0.16; 'subject:robots': 0.16; 'wrote:': 0.16; 'implementing': 0.18; '(in': 0.18; 'language': 0.19; '>>>': 0.20; 'algorithm': 0.20; 'lawrence': 0.22; 'am,': 0.23; 'code,': 0.23; 'sat,': 0.23; 'header:In-Reply-To:1': 0.24; 'header:User-Agent:1': 0.26; 'header:X-Complaints-To:1': 0.26; 'connected': 0.27; 'checking': 0.27; 'coding': 0.27; 'joe': 0.27; 'cells': 0.29; 'url:wikipedia': 0.29; 'print': 0.30; 'url:wiki': 0.30; "i'd": 0.31; 'post': 0.31; 'anyone': 0.32; 'implement': 0.32; 'language.': 0.32; 'run': 0.33; 'equal': 0.34; 'could': 0.35; 'direction': 0.35; 'comment': 0.35; 'step': 0.36; 'but': 0.36; 'needed': 0.36; 'url:org': 0.36; 'to:addr:python-list': 0.36; 'subject:: ': 0.37; 'received:org': 0.37; 'thought': 0.37; 'data': 0.39; 'url:en': 0.39; 'subject:the': 0.39; 'build': 0.40; 'to:addr:python.org': 0.40; 'where': 0.40; 'mark': 0.40; 'some': 0.40; 'field': 0.60; 'reach': 0.61; 'charset:windows-1252': 0.62; 'distance': 0.63; 'movement': 0.63; 'saturday,': 0.63; 'our': 0.64; 'between': 0.65; 'legal': 0.66; 'direct': 0.68; 'choose': 0.68; 'sum': 0.69; 'centers': 0.72; 'walk': 0.72; 'transfer': 0.73; 'pythonistas,': 0.84; 'reachable': 0.84; 'standing': 0.84; 'comment.': 0.91; 'robot': 0.91; 'steps.': 0.91; 'divided': 0.93 X-Injected-Via-Gmane: http://gmane.org/ X-Gmane-NNTP-Posting-Host: 80.234.134.43 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 In-Reply-To: X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Mailman-Original-Message-ID: X-Mailman-Original-References: <8c570da8-ab31-44f3-9fdf-83e28741ffe4@googlegroups.com> Xref: csiph.com comp.lang.python:106757 On 09/04/2016 18:13, Joe wrote: > On Saturday, 9 April 2016 18:44:20 UTC+2, Ian wrote: >> On Sat, Apr 9, 2016 at 8:18 AM, Joe wrote: >>> How to find the number of robots needed to walk through the rectangular grid >>> The movement of a robot in the field is divided into successive steps >>> >>> In one step a robot can move either horizontally or vertically (in one row or in one column of cells) by some number of cells >>> >>> A robot can move in one step from cell X to cell Y if and only if the distance between the centers of the cells X and Y is equal to the sum of integers contained in X and Y >>> >>> Cell X is reachable for robot A if either A is currently standing in the cell X or A can reach X after some number of steps. During the transfer the robot can choose the direction (horizontal or vertical) of each step arbitrarily >>> [![enter image description here][1]][1] >>> >>> I started implementing it by first checking the row and print the index of the Cell X and Y where the distance is equal to the sum of integers contained in X and Y >>> >>> but after coding I found it difficult to remember the index when moving vertically >>> >>> So I thought to Build a graph where nodes are grid cells and edges are legal direct movements, then run any connected components algorithm to find which cells are reachable from each other >>> >>> >>> Can anyone implement it with graphs or queue? >> >> I'd use a disjoint-set data structure. The number of robots needed is >> equal to the number of disjoint subsets. >> >> https://en.wikipedia.org/wiki/Disjoint-set_data_structure > > Could you post a formal solution of disjoint-set using my algorithm > You write the code, we comment on it. No code, no comment. Got the message? -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence