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Programming Puzzle 25 - The Great Escape

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  • Tom Cone Jr
    replied
    Re: Programming Puzzle 25 - The Great Escape

    Stephen,

    Very nice! The "professor" likes your second solution. Good work. Hope you enjoyed the exercise!

    Leave a comment:


  • StephenP
    replied
    Re: Programming Puzzle 25 - The Great Escape

    Professor,

    By the way, I didn't look at your result until after I took the test.

    Leave a comment:


  • StephenP
    replied
    Re: Programming Puzzle 25 - The Great Escape

    Professor:

    My simple, uncommented code:

    Code:
    dim cellblock[100] as l
    for g = 1 to 100
    	for c = 1 to 100 step g
    		cellblock[c] = iif(cellblock[c], .f., .t.)
    	next c
    next g
    for c = 1 to 100
    	iif(cellblock[c],trace.writeln(c+": Open"),"")
    next c
    and with my comments:

    Code:
    'All cellblocks are locked by default (.f.):
    dim cellblock[100] as l
    'work through each of the 100 guards:
    for g = 1 to 100
    	'visiting each of the 100 cellblocks:
    	for c = 1 to 100 step g
    		'unlocking, if locked, and vice versa:
    		cellblock[c] = iif(cellblock[c], .f., .t.)
    	'visiting the next cellblock:
    	next c
    'moving on to the next guard:
    next g
    'checking all 100 cellblocks:
    for c = 1 to 100
    	'tracing out only the unlocked cells:
    	iif(cellblock[c],trace.writeln(c+": Open"),"")
    next c
    In the end, I had nine cellblocks open:

    2: Open
    5: Open
    10: Open
    17: Open
    26: Open
    37: Open
    50: Open
    65: Open
    82: Open

    Ah, but what if the guards each started, not at cellblock 1, but cellblock N:

    Code:
    'All cellblocks are locked by default (.f.):
    dim cellblock[100] as l
    'work through each of the 100 guards:
    for g = 1 to 100
    	'visiting each of the 100 cellblocks:   ***** Note that each guard starts at cellblock N *****
    	for c = g to 100 step g
    		'unlocking, if locked, and vice versa:
    		cellblock[c] = iif(cellblock[c], .f., .t.)
    	'visiting the next cellblock:
    	next c
    'moving on to the next guard:
    next g
    'checking all 100 cellblocks:
    for c = 1 to 100
    	'tracing out only the unlocked cells:
    	iif(cellblock[c],trace.writeln(c+": Open"),"")
    next c
    Now we end up with ten cellblocks open:

    1: Open
    4: Open
    9: Open
    16: Open
    25: Open
    36: Open
    49: Open
    64: Open
    81: Open
    100: Open

    Leave a comment:


  • Tom Cone Jr
    replied
    Re: Programming Puzzle 25 - The Great Escape

    Andrew, I don't understand your point. I must be missing something. The puzzle specifies that each guard must either open or close (lock or unlock) each cell door he or she visits.

    Leave a comment:


  • aschone
    replied
    Re: Programming Puzzle 25 - The Great Escape

    Code:
    if cells[x] = 0 then
    	cells[x] = 1
    else
    	cells[x] = 0	
    end if
    I believe all three solutions used something similar to this if..else.. end if.

    This could have shortened saving a assignment of the value 0 (locked) to the cell array element. In other words, if the cell is already locked why relock it?

    Code:
    if cells[x] = 0 then
    	cells[x] = 1
    end if

    Leave a comment:


  • Tom Cone Jr
    replied
    Re: Programming Puzzle 25 - The Great Escape

    And, here's Tom's solution.

    I used a For ... Next code block with a variable STEP parameter to do the heavy lifting.

    Comments? Questions? Corrections?

    Leave a comment:


  • Tom Cone Jr
    replied
    Re: Programming Puzzle 25 - The Great Escape

    gandhi,

    Nice!

    -- tom

    Leave a comment:


  • GGandhi
    replied
    Re: Programming Puzzle 25 - The Great Escape

    okay tom
    here is the corrected one

    Code:
    dim x as n
    dim cell[100] as c
    for x=1 to 100
    	cell[x]="locked"
    	next x
    dim guard as n
    dim doorNumber as n
    
    	for doorNumber = 1 to 100 'guard will visit all the doors
    		for guard = 1 to 100
    		
    			if mod(doorNumber,guard)=0 then ' but enter only few
    				if cell[doorNumber]="locked" then 
    				    cell[doorNumber]="open"
    				    else
    				    cell[doorNumber]="locked"
    				end if
    			end if
    		next 
    	next 
    		
    dim count as n
    trace.clear()
    for i = 1 to 100
    	if cell[i]="open"
    		trace.writeln("Cell number "+ i +" was left open")
    		count = count+1
    	end if
    next
    trace.writeln("Total of "+count+" prisoners will escape")
    'msgbox("Open cells",str(count))
    end

    Leave a comment:


  • Tom Cone Jr
    replied
    Re: Programming Puzzle 25 - The Great Escape

    gandhi,

    No problem. That's why they're called "puzzles" !

    Have fun sorting it out.

    -- tom

    Leave a comment:


  • Keith Hubert
    replied
    Re: Programming Puzzle 25 - The Great Escape

    All my guards came out on strike!!!

    Leave a comment:


  • Tom Cone Jr
    replied
    Re: Programming Puzzle 25 - The Great Escape

    Keith, you're on the right path. Only 90 more guards to go!

    Leave a comment:


  • GGandhi
    replied
    Re: Programming Puzzle 25 - The Great Escape

    hello

    thanks
    i looked at the result of both solutions presented and
    the outcome from mine was wrong. while total remains correct.(different prisoners will get out)
    will need to clean up the thinking process.

    thanks again

    Leave a comment:


  • Keith Hubert
    replied
    Re: Programming Puzzle 25 - The Great Escape

    Manually I have
    1=open
    2=locked
    3=locked
    4=open
    5=locked
    6=locked
    7=locked
    8=locked
    9=open
    and 10 = locked

    Which is the same as Andrew's solution. (His is better than mine as it goes all the way).

    Leave a comment:


  • Tom Cone Jr
    replied
    Re: Programming Puzzle 25 - The Great Escape

    Gandhi,

    The professor applauds your effort, but has a couple of small bones to pick with you.

    I don't fully understand his comments, but maybe they'll mean something to you.

    Your code:
    Code:
    pass = 1
    while pass < 100
    	for guard = 1 to 100 step pass
    	    if cell[guard]="open" then
    	        cell[guard]="locked"
    	    else
    	        cell[guard]="open"
    	    end if
    	next guard
            pass = pass + 1
    end while
    1) The professor thinks your While ... End While code block never reaches the 100th guard, since the block is exited when pass equals 100.

    2) In the For ... Next block the professor insists that all 100 guards visit door 1, when only guard #1 should visit that cell.

    3) The professor applauds your use of the "step" parameter in the For ... Next block. Very clever, grasshopper!

    Leave a comment:


  • GGandhi
    replied
    Re: Programming Puzzle 25 - The Great Escape

    hello
    the cell number 1 should have been left open but in mine it was closed. so i changed to while...end while and now the result is 10, which i think is correct.

    Code:
    dim n as n
    dim cell[100] as c
    for n = 1 to 100
    	cell[n]="locked"
    	'trace.writeln(cell[n]+crlf())
    	next n
    dim guard as n
    dim pass as n
    pass = 1
    while pass < 100
    	for guard = 1 to 100 step pass
    	if cell[guard]="open" then
    	    cell[guard]="locked"
    	    else
    	    cell[guard]="open"
    	end if
    		next guard
    pass = pass + 1
    end while
    dim open as n=0
    dim i as n
    trace.clear()
    for i = 1 to 100
    	if cell[i]="open" then
    		trace.writeln("cell number " + i + " was left open")
    	    open = open+1
    	end if
    	next
    		trace.writeln("Total number of " + open + " prisioners will escape")
    	'msgbox("Open Cells",str(open) + " Prisioners will escape when all is done")
    	end

    Leave a comment:

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