Algorithm Exercise

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Summary:

I'm trying to understand the basic number search algorithm by programming it on my calc, but I'm having trouble.

Algorithm Exercise

Sitay Huber 09 Mar 2021 16:26

I'm working on a basic binary number search algorithm. I'm learning computer science, and figured the TI-84 should be able to do this type of algorithm.

You might want to skim the code before continuing, so you understand what I'm saying.

The code runs fine if I say the number ("N") is correct, (press 1, and it displays "Woo hoo!"), or when I tell it the number is lower, (it sets the returned number as the upper limit, and re-runs the equation). But when I try to tell it my desired number is *higher,* it all falls apart, and just returns the same number again. Example:

I set "H" to 100, "L" to 0, and let it run. Calculator returns N, which is 50. When I tell it to go higher, (input "2"), the calculator returns 50 again. The only way I can explain that, is that it's putting "50" in both "H" and "L", which makes no sense. How do I tell it to keep one number the same, and only reset the one I'm telling it to?

Here's the code:
ClrHome
Disp "LOW LIMIT"
Prompt L
Disp "HIGH LIMIT"
Prompt H
Lbl 1
(H+L)/2→N
Disp "CORRECT?",N
Disp "1 IF YES"
Disp "0 IF LOWER"
Disp "2 IF HIGHER"
Prompt A
If A=1
Goto 2
If A=0
N→H
Goto 1
If A=2
N→L
Goto 1
Lbl 2
Disp "WOO HOO!"
Pause
ClrHome

Also, if you know how I could get the calculator to round "N" to the nearest integer, I would appreciate that. Something with the "round(" function, right?

P.S. Please do not tell me to go download an program, or copy someone else's. I'm not doing this to actually utilize program, I'm doing this to learn how these things work.

Last edited on 09 Mar 2021 16:27 by Sitay Huber Show more

Re: Algorithm Exercise

Trenly 09 Mar 2021 17:23

Welcome to TI|BD

It seems your issue is because an if statement only executes the first line after it unless it is an If-Then-End block. It will always encounter the "Goto 1" before it checks if A is equal to 2

The other problem you will have is with Memory Leaks. If you do put in an If-Then-End, using Goto inside of the "Then" section causes a memory leak. When possible, you should try to use while loops and repeat loops. If you want to see an example of how I would write the algorithm you have, avoiding memory leaks, here it is:

+Show Code

Here is how I would write the algorithm you have, using Piecewise expressions:

ClrHome
0→A
Input "LOW LIMIT: ",L
Input "HIGH LIMIT: ",H
While A≠1
  (H+L)/2→N
  Disp "CORRECT?",N
  Disp "1 IF YES"
  Disp "0 IF LOWER"
  Disp "2 IF HIGHER"
  Prompt A
  N(A=0)+Hnot(A=0)→H
  N(A=2)+Lnot(A=2)→L
End
Pause "WOO HOO!"
ClrHome

Here is another way to do it using the + - and Enter keys for control:

ClrHome
0→K
Input "LOW LIMIT: ",L
Input "HIGH LIMIT: ",H
While K≠105
  mean({H,L→N
  Disp "CORRECT?",N
  Disp "+/-/Enter"
  Repeat sum(K={105,95,85
    getKey→K
  End
  N(K=85)+H(K≠85)→H
  N(K=95)+L(K≠95)→L
End
Pause "WOO HOO!"
ClrHome

Last edited on 09 Mar 2021 17:25 by Trenly Show more

Re: Algorithm Exercise

Sitay Huber 09 Mar 2021 18:26

Great, thank you very much! I think I understand it better now.