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coding problem : Mars rovers

Claire Fuente
Ranch Hand

Joined: Feb 07, 2004
Posts: 35
Hi Guys!

I need a code that works on a sample problem below. I am not a good java programmer and I'm trying to do it too but my solution might be incorrect. You may not use any external libraries to solve this problem, but you may use external libraries or tools for building or testing purposes. Specifically, you may use unit testing libraries or build tools available for your chosen language (e.g., JUnit, Ant, NUnit, Rspec, Rake, etc.)

Thank you for your help.


A squad of robotic rovers are to be landed by NASA on a plateau on Mars. This plateau, which is curiously rectangular, must be navigated by the rovers so that their on-board cameras can get a complete view of the surrounding terrain to send back to Earth.

A rover's position and location is represented by a combination of x and y co-ordinates and a letter representing one of the four cardinal compass points. The plateau is divided up into a grid to simplify navigation. An example position might be 0, 0, N, which means the rover is in the bottom left corner and facing North.

In order to control a rover, NASA sends a simple string of letters. The possible letters are 'L', 'R' and 'M'. 'L' and 'R' makes the rover spin 90 degrees left or right respectively, without moving from its current spot. 'M' means move forward one grid point, and maintain the same heading.

Assume that the square directly North from (x, y) is (x, y+1).

The first line of input is the upper-right coordinates of the plateau, the lower-left coordinates are assumed to be 0,0.

The rest of the input is information pertaining to the rovers that have been deployed. Each rover has two lines of input. The first line gives the rover's position, and the second line is a series of instructions telling the rover how to explore the plateau.

The position is made up of two integers and a letter separated by spaces, corresponding to the x and y co-ordinates and the rover's orientation.

Each rover will be finished sequentially, which means that the second rover won't start to move until the first one has finished moving.

The output for each rover should be its final co-ordinates and heading.


Test Input:
5 5
1 2 N
3 3 E

Expected Output:
1 3 N
5 1 E
Kristjan Toots
Ranch Hand

Joined: Jun 03, 2011
Posts: 59

Cmon, we've already answered to your #1 post and we said what you should do.

Please correct my english.
Campbell Ritchie

Joined: Oct 13, 2005
Posts: 39415
You will find life much simpler if you complete one assignment at a time. What you learn from one will help you solve the others. Try the tax example first.
Claire Fuente
Ranch Hand

Joined: Feb 07, 2004
Posts: 35
Campbell Ritchie wrote:You will find life much simpler if you complete one assignment at a time. What you learn from one will help you solve the others. Try the tax example first.

I'm trying to do your advice and wrote down the possible modules needed in this problem. I also thought of starting with the sales tax problem since I find it easiest to analyze. However, I'm stuck on the formula on how I would do a syntax on

"The rounding rules for sales tax are that for a tax rate of n%, a shelf price of p contains (np/100 rounded up to the nearest 0.05) amount of sales tax. "

Sorry but I'm not good in math .

I got the output right on sample:

Given :
Basic tax = 10%
import duty is additional = 5% no exemptions

1 imported bottle of perfume at 27.99 x (10%+5%) = 4.2

27.99 + 4.2 = 32.19

Output 3:
1 imported bottle of perfume: 32.19

But got a different answer when the input is:
1 imported bottle of perfume at 47.50 x (10%+5%) = 7.125

47.5 + 7.125 = 54.625

Expected output is :
1 imported bottle of perfume: 54.65

Henry Wong

Joined: Sep 28, 2004
Posts: 18896

This seems to be a duplicate of your other topic...

Books: Java Threads, 3rd Edition, Jini in a Nutshell, and Java Gems (contributor)
I agree. Here's the link:
subject: coding problem : Mars rovers