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Nov 3rd, 2009

Correcting inefficiency in pseudocode

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I have been asked to find the inefficiency in a piece of pseducode. I've looked at it but can't see it.

IF count > 10 THEN
WHILE x < 0 DO
INPUT x
ENDWHILE
ENDIF

My understanding:
Count is evaluated. If count is <10, the app moves onto the next section. If count is > 10, X is evaluated. Until x is <0, the user will keep being prompted to input x. Once they input x>=0, the loop finishes.

Please note: this is one question on a mock test - it is the whole code. I'm supposed to find the problem with this snippet. eg. there is no mention of x being a value outside of the IF section.

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tom.t

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Nov 3rd, 2009

Re: Correcting inefficiency in pseudocode

. check x on input, where x is old
. if x >=0, INPUT never occurs, then x remain forever old >= 0 value

quuba

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Nov 3rd, 2009

Re: Correcting inefficiency in pseudocode

Click to Expand / Collapse Quote originally posted by tom.t ...

IF count > 10 THEN
WHILE x < 0 DO
INPUT x
ENDWHILE
ENDIF

My understanding:
Count is evaluated. If count is <10, the app moves onto the next section. If count is > 10, X is evaluated. Until x is <0, the user will keep being prompted to input x. Once they input x>=0, the loop finishes.

Also, what I'm seeing is that if count has an inital value less than 10, it looks like it will stay that way. Look at the code again and ask, "How will my final condition (count being greater than or equal to 10) be satisfied? Because I don't see it in this sample. (hint: where is count incremented?)

eggmatters

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Nov 3rd, 2009

Re: Correcting inefficiency in pseudocode

Thank you both for your suggestions. I think I was a bit thrown by the abstract nature of the question but what you both say makes sense.

tom.t

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Nov 4th, 2009

Correcting inefficiency in pseudocode

I tried the following code which is inline with the pseudo code in the original code which works fine.
I dont see any errros in the pseudo code.

java Syntax (Toggle Plain Text)
int count = 11;
		int x = -1;
		if(count > 10) {
			while( x < 0) {
			try {
					x = x - 1;
					System.out.println("inside while ");
			      } catch (Exception ioe) {
			         System.out.println("IO error trying to read your name!");
 
			      }
			}
		}
int count = 11;
		int x = -1;
		if(count > 10) {
			while( x < 0) {
			try {
					x = x - 1;
					System.out.println("inside while ");
			      } catch (Exception ioe) {
			         System.out.println("IO error trying to read your name!");
			         
			      }
			}
		}

Last edited by peter_budo; Nov 4th, 2009 at 5:25 am. Reason: Keep It Organized - For easy readability, always wrap programming code within posts in [code] (code blocks)

shobhit123

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Nov 4th, 2009

Re: Correcting inefficiency in pseudocode

Thanks for that.

I think the question is trying to get us to think about efficiency rather than correcting an error. At least, that's my guess based on the wording.

tom.t

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Nov 4th, 2009

Re: Correcting inefficiency in pseudocode

Click to Expand / Collapse Quote originally posted by shobhit123 ...

I tried the following code which is inline with the pseudo code in the original code which works fine.
I dont see any errros in the pseudo code.
java Syntax (Toggle Plain Text)
int count = 11;
		int x = -1;
		if(count > 10) {
			while( x < 0) {
			try {
					x = x - 1;
					System.out.println("inside while ");
			      } catch (Exception ioe) {
			         System.out.println("IO error trying to read your name!");
 
			      }
			}
		}
int count = 11; int x = -1; if(count > 10) { while( x < 0) { try { x = x - 1; System.out.println("inside while "); } catch (Exception ioe) { System.out.println("IO error trying to read your name!"); } } }

The code wasn't in "error" so to speak. He was asked to find the inefficiencies with it. When you ran your program, how did you end it? Did the program exit gracefully?

eggmatters

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Nov 4th, 2009

Re: Correcting inefficiency in pseudocode

If you were to assume the "count" is incremented in another loop, you could have the test for the value of "count" exit sooner, which could potentially be more efficient depending on the size of the test for "x"

IF count > 10 THEN
WHILE x < 0 DO
INPUT x
ENDWHILE
ENDIF

...becomes...

IF count > 10 THEN
CONTINUE // or return
ENDIF

WHILE x < 0 DO
INPUT x
ENDWHILE

thines01

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Nov 4th, 2009

Re: Correcting inefficiency in pseudocode

Another good suggestion. Everyone has given me a lot to think about, and a good chance of answering the question (which will of course be different) on the exam.

tom.t

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