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Topic: 2 Robots (Read 3516 times) |
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mad
Junior Member
Posts: 118
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Two robots are standing on an infinitely long line at infinte unknown positions. We need to make them meet. To do so, we need to write same program for both of them using statements
MOVL (move 1 step left)
MOVR (move 1 step right)
MOV2L (move 2 steps left)
MOVR (move 2 steps right)
MARK (make a mark at current position)
if( Mark ) //True if mark is already there.
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Icarus
wu::riddles Moderator
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Re: 2 Robots
« Reply #1 on: Mar 8th, 2008, 7:26am » |
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No negation or Else operators? No branching instructions? That will require infinitely long programs.
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Hippo
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Re: 2 Robots
« Reply #2 on: Mar 8th, 2008, 7:54am » |
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It is very simillar to hole in the wall ... one of the robots will stand still mimicking the hole...
Yes, some variables will be helpful ... what about unmarking, conditioanl loops, branching ...
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| « Last Edit: Mar 8th, 2008, 7:55am by Hippo » |
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rmsgrey
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Re: 2 Robots
« Reply #3 on: Mar 8th, 2008, 8:00am » |
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on Mar 8th, 2008, 7:54am, Hippo wrote:It is very simillar to hole in the wall ... one of the robots will stand still mimicking the hole...
Yes, some variables will be helpful ... what about unmarking, conditioanl loops, branching ... |
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You can't have just one robot stand still throughout - each robot has the same program...
I'd go for:
MOVL
if ( Mark ) MOV2L
MARK
repeated infinitely many times...
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Hippo
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Re: 2 Robots
« Reply #4 on: Mar 8th, 2008, 10:37am » |
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Oops: one letter difference sAme not sOme 
And yes, your solution works well if the conditions are interpreted the way you use.
(Suppose originaly there is sufficient number of places with no marks )
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| « Last Edit: Mar 8th, 2008, 10:41am by Hippo » |
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Grimbal
wu::riddles Moderator
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Re: 2 Robots
« Reply #5 on: Mar 9th, 2008, 6:16am » |
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What is missing in the question is: how are the robots synchronized. Do they repeat the whole program with each time tick? Do they repeat one instruction per time tick? If yes, is if ( ... ) ... executed in one or two ticks when the condition is true?
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temporary
Full Member
Posts: 255
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Re: 2 Robots
« Reply #6 on: Mar 23rd, 2008, 1:24pm » |
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Write this program for only one(or possibly both) robot(s):
MOVL
MOV2R
MOV3L
MOV4R
MOV5L
MOV6R...
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rmsgrey
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Re: 2 Robots
« Reply #7 on: Mar 24th, 2008, 2:19pm » |
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on Mar 23rd, 2008, 1:24pm, temporary wrote:Write this program for only one(or possibly both) robot(s):
MOVL
MOV2R
MOV3L
MOV4R
MOV5L
MOV6R... |
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There are two problems with that program. Firstly, it uses instructions that aren't included in the initial set, which only allows for moves of up to 2 steps. Secondly, if both robots execute it at the same speed, there will always be a constant distance between them.
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temporary
Full Member
Posts: 255
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Re: 2 Robots
« Reply #8 on: Mar 25th, 2008, 6:09pm » |
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Then I suppose programming both of them wouldn't work, but programming only one of them still works. And I can still use that answer by simply rewriting it with only two steps at a time.
MOVL
MOV2R
MOV2L
MOVL
MOV2R
MOV2R
MOV2L
MOV2L
MOVL
MOV2R
MOV2R
MOV2R
MOV2L...
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rmsgrey
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Re: 2 Robots
« Reply #9 on: Mar 26th, 2008, 12:45pm » |
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on Mar 25th, 2008, 6:09pm, temporary wrote:Then I suppose programming both of them wouldn't work, but programming only one of them still works. And I can still use that answer by simply rewriting it with only two steps at a time.
MOVL
MOV2R
MOV2L
MOVL
MOV2R
MOV2R
MOV2L
MOV2L
MOVL
MOV2R
MOV2R
MOV2R
MOV2L... |
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It's possible for the two robots to be guaranteed to meet, despite both running the same program. The key is the if command that lets the robots behave differently depending on whether they are at marked positions or not.
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Hippo
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Re: 2 Robots
« Reply #10 on: Mar 26th, 2008, 3:11pm » |
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rmsgrey: Nice to see someone who is able to comment the posts in such a polite way.
I myself should ignore them not having enough mental powers to be able to ...
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marsh8472
Newbie
Posts: 27
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Re: 2 Robots
« Reply #11 on: Sep 14th, 2012, 1:39am » |
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on Mar 7th, 2008, 8:11pm, mad wrote:Two robots are standing on an infinitely long line at infinte unknown positions. We need to make them meet. To do so, we need to write same program for both of them using statements
MOVL (move 1 step left)
MOVR (move 1 step right)
MOV2L (move 2 steps left)
MOVR (move 2 steps right)
MARK (make a mark at current position)
if( Mark ) //True if mark is already there. |
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do until MARK
MOVL
LOOP
do until MARK == false
MOV2L
loop
They both move left until they pick up the other's trail then once the rightmost bot picks up the leftmost bot's trail, the rightmost bot moves twice the speed until it catches up with the leftmost bot.
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