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Simple Algorithm Exercise by frankg1(m): 8:18pm On Sep 24, 2017 |
Once upon a time, on a way through the old wild west,… … a man was given directions to go from one point to another. The directions were "NORTH", "SOUTH", "WEST", "EAST". Clearly "NORTH" and "SOUTH" are opposite, "WEST" and "EAST" too. Going to one direction and coming back the opposite direction is a needless effort. Since this is the wild west, with dreadfull weather and not much water, it's important to save yourself some energy, otherwise you might die of thirst! How I crossed the desert the smart way. The directions given to the man are, for example, the following: ["NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH", "WEST"]. or { "NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH", "WEST" }; or (haskell) [North, South, South, East, West, North, West] You can immediatly see that going "NORTH" and then "SOUTH" is not reasonable, better stay to the same place! So the task is to give to the man a simplified version of the plan. A better plan in this case is simply: ["WEST"] or { "WEST" } or (haskell) [West] or (rust) [WEST]; Other examples: In ["NORTH", "SOUTH", "EAST", "WEST"], the direction "NORTH" + "SOUTH" is going north and coming back right away. What a waste of time! Better to do nothing. The path becomes ["EAST", "WEST"], now "EAST" and "WEST" annihilate each other, therefore, the final result is [] (nil in Clojure). In ["NORTH", "EAST", "WEST", "SOUTH", "WEST", "WEST"], "NORTH" and "SOUTH" are not directly opposite but they become directly opposite after the reduction of "EAST" and "WEST" so the whole path is reducible to ["WEST", "WEST"]. Task Write a function dirReduc which will take an array of strings and returns an array of strings with the needless directions removed (W<->E or S<->N side by side). The Haskell version takes a list of directions with data Direction = North | East | West | South. The Clojure version returns nil when the path is reduced to nothing. The Rust version takes a slice of enum Direction {NORTH, SOUTH, EAST, WEST}. Examples dirReduc({"NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH", "WEST"}) => {"WEST"} dirReduc({"NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH"}) => {} See more examples in "Example Tests" Note Not all paths can be made simpler. The path ["NORTH", "WEST", "SOUTH", "EAST"] is not reducible. "NORTH" and "WEST", "WEST" and "SOUTH", "SOUTH" and "EAST" are not directly opposite of each other and can't become such. Hence the result path is itself : ["NORTH", "WEST", "SOUTH", "EAST"]. 1 Like |
Re: Simple Algorithm Exercise by nsimageorge(m): 10:02pm On Sep 24, 2017 |
Using JavaScript function dirReduc(arr){ var string = arr.join( " " ); var wrongMatch = /NORTHSOUTH|SOUTHNORTH|EASTWEST|WESTEAST/; while(wrongMatch.test(string)) { string = string.replace(wrongMatch, ''); } return string.match(/NORTH|SOUTH|EAST|WEST/) || []; } |
Re: Simple Algorithm Exercise by yorex2011: 9:54pm On Sep 25, 2017 |
Isnt this a case of just removing pairs of opposing directions till you are left with one or none...? |
Re: Simple Algorithm Exercise by frankg1(m): 10:43pm On Sep 25, 2017 |
nsimageorge: Your code didnt pass it... sorry |
Re: Simple Algorithm Exercise by nsimageorge(m): 7:52pm On Sep 26, 2017 |
frankg1: https://codepen.io/nsimageorge/pen/VMpeVB This is my solution on code pen... How did it not pass?? |
Re: Simple Algorithm Exercise by frankg1(m): 8:27pm On Sep 26, 2017 |
nsimageorge: run it here https://www.codewars.com/kata/directions-reduction/train/javascript. that is where i got the question from |
Re: Simple Algorithm Exercise by nsimageorge(m): 8:50pm On Sep 26, 2017 |
frankg1:Okay, I see my mistake function dirReduc(arr){ var string = arr.join( '' ); var wrongMatch = /NORTHSOUTH|SOUTHNORTH|EASTWEST|WESTEAST/; while(wrongMatch.test(string)) { string = string.replace(wrongMatch, ''); } return string.match(/NORTH|SOUTH|EAST|WEST/g) || []; } |
Re: Simple Algorithm Exercise by orimion(m): 7:23pm On Sep 27, 2017 |
Haskell
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Re: Simple Algorithm Exercise by escapefromusa(f): 1:51am On Sep 28, 2017 |
Not clear what to do. Do we . Take a dir.. like go north, then we can't got north again? |
Re: Simple Algorithm Exercise by deedat205(m): 11:24am On Sep 29, 2017 |
orimion and Haskell are 5 and 6 def dirReduc(l): cor = ['NORTH','SOUTH','WEST','EAST'] i = 0 while i < len(l)-1: if l[i] == cor[0] and l[i+1] == cor[1] or l[i] == cor[1] and l[i+1] == cor[0]: del(l[i]) del(l[i]) i = 0 elif l[i] == cor[2] and l[i+1] == cor[3] or l[i] == cor[3] and l[i+1] == cor[2]: del(l[i]) del(l[i]) i = 0 else: i += 1 return l |
Re: Simple Algorithm Exercise by frankg1(m): 9:05am On Sep 30, 2017 |
orimion: i dont understand this haskell one bit... but it works though |
Re: Simple Algorithm Exercise by orimion(m): 3:41pm On Sep 30, 2017 |
deedat205:don't you just love how it reads frankg1:http://learnyouahaskell.com it'll challenge everything you know about programming |
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