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Topic: copy paste problem (Read 1724 times) |
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alexeigor
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Posts: 45
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copy paste problem
« on: Jan 20th, 2011, 8:39am » |
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Write a program to print the sequence of keystrokes such that it generates the maximum number of character 'A's. You are allowed to use only 4 keys: A, Ctrl+A, Ctrl+C and Ctrl+V. Only N keystrokes are allowed. All Ctrl+ characters are considered as one keystroke, so Ctrl+A is one keystroke.
For example, the sequence A, Ctrl+A, Ctrl+C, Ctrl+V generates two A's in 4 keystrokes.
* Ctrl+A is Select All
* Ctrl+C is Copy
* Ctrl+V is Paste
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towr
wu::riddles Moderator
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Re: copy paste problem
« Reply #1 on: Jan 20th, 2011, 9:52am » |
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function foo(n)
{
a = [0,1,2,3,4,5,6,9,12,16,20,27,36,48,64,81];
if ( n <= 15 )
return a[n];
else
n -= 11;
d = n % 5;
f = (n-d)/5;
return a[d+11] << (2*f);
}
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birbal
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Re: copy paste problem
« Reply #2 on: Jan 25th, 2011, 5:20am » |
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on Jan 20th, 2011, 9:52am, towr wrote:function foo(n)
{
a = [0,1,2,3,4,5,6,9,12,16,20,27,36,48,64,81];
if ( n <= 15 )
return a[n];
else
n -= 11;
d = n % 5;
f = (n-d)/5;
return a[d+11] << (2*f);
}
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Nice solution  . Can you explain how did you reach at this solution ? ( As in by mere observation of the series or any mathematical way ? )
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towr
wu::riddles Moderator
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Re: copy paste problem
« Reply #3 on: Jan 25th, 2011, 9:04am » |
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By mere observation.
For good measure, it really ought to be proved correct. Maybe I'll get around to that eventually.
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birbal
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Re: copy paste problem
« Reply #4 on: Jan 27th, 2011, 4:28am » |
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i think we can form a recurrence relation and solve it. Need to work out what exactly is to be done.
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Grimbal
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Re: copy paste problem
« Reply #5 on: Jan 28th, 2011, 8:40am » |
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One thing still bothers me. As I know it,
- ctrl-C copies the selected text to the paste buffer without unselecting it
- ctrl-V replaces the selected text with the paste buffer
So, the sequence A, ctrl-A, ctrl-C leaves one A selected, and ctrl-V replaces it with the A from the paste buffer. It doesn't result in 2 A's.
I daily duplicate lines of text by selecting the lines and pressing ctrl-C, ctrl-V, ctrl-V. The first ctrl-V having the effect of unselecting the selection.
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towr
wu::riddles Moderator
Uberpuzzler
Some people are average, some are just mean.
Gender:
Posts: 13730
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Re: copy paste problem
« Reply #6 on: Jan 28th, 2011, 11:48am » |
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It would depend on the editor.
In any case, you can consider that you are given 4 operations to work with, and "replace" is not among them (nor implied by their description).
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