Programming Puzzle 25 - The Great Escape

[GGandhi]

Re: Programming Puzzle 25 - The Great Escape

hello
here is my solution. but somehow i am getting 9. i do not know why.

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
for pass = 1 to 100
	for guard = 1 to 100 step pass
	if cell[guard]="locked" then
	    cell[guard]="open"
	    else
	    cell[guard]="locked"
	end if
		next guard
next pass
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

[Keith Hubert]

Re: Programming Puzzle 25 - The Great Escape

Hi Andrew,

This looks much better. This puzzle is along the lines of Josephus Problem.

[aschone]

Re: Programming Puzzle 25 - The Great Escape

Second go; first had a few mistakes. Am very curious to see what others come up with for a solution.

[Keith Hubert]

Re: Programming Puzzle 25 - The Great Escape

Andy, Looks good to me. However, working it out on paper with only 10 and 10, I get 5 and 5. So I imagine the 50% would be the same for 100 ?

[aschone]

Re: Programming Puzzle 25 - The Great Escape

Chances are good my calculation is wrong but I am sure the Professor will be kind enough to correct me.

[aschone]

Re: Programming Puzzle 25 - The Great Escape

doh! I withdraw my previous question.

[Tom Cone Jr]

Re: Programming Puzzle 25 - The Great Escape

Andrew, have a cup of coffee, then read the first line of the puzzle carefully.

-- tom

[aschone]

Re: Programming Puzzle 25 - The Great Escape

What is the status of the doors prior to the first guard checking?

[Tom Cone Jr]

' There are 100 prisoners in 100 separate locked cells.
' There are 100 guards who visit the cells during the night.
' The first guard visits all 100 cells.
' The second guard visits every other cell.
' The third guard visits every third cell.
' ... and so on
' Until, finally, the 100th guard visits the 100th cell.
'
' Now here's the catch. When a guard visits a cell he or she
' locks the cell door if it's open, and unlocks the cell door
' if it's locked.
'
' After the last guard has done his duty, prisoners in cells
' with open (unlocked) doors can escape. In the morning,
' how many prisoners have escaped? For extra credit can
' you tell us which cells were left open?
'
' Write your answer to the trace window.
'
' Have fun!
'
' Credit plus.maths.org