Nested while loop problem

Programming Questions

HartyFart..

in Programming Questions • 3 years ago

Hi all,

I have an issue, It goes a little something like this:

while(true){

while(a && !b && !c){ // nested 1

while(a && b && !c){ // nested 2

while(a && b && c){ // nested 3

Do stuff!

}

a, b and c are user inputs and any combination of them can be true at any time,

I'm looking for the correct combination from the user...

Am I right in thinking that when the code gets to nested loop 2 as soon

as b becomes true I will get kicked out of nested loop 1 as !b is no longer satisfied?

I have it running on a separate thread as I want it to always be checking this,

the program has reached ''do stuff! but it is seldom an occurrence.......

If anyone has a fix or alternative please help

P.S. This is my first post, so bare with me if I am breaking any forum rules..

Replies(4)

PhiLho

No. The code will remain in loop 2 as long as the conditions are true, and the conditions for loop 1 will be checked only when going out of loop 2.
Maybe you want to use ifs instead of whiles? The code seems a bit odd like this.
Don't forget the break and continue keywords too, they can be precious!

HartyFart..

Re: Re: Nested while loop problem

3 years ago

Thanks for the help,

I played around with it a bit, its a horrible hack job now, but it seems to work.... if very slowly

while(true){ // first loop

if (a && !b && !c){

while(true){

if (a && b && !c){

while(true){

if(a && b && c){

Do stuff!

break;

}

Is there a way to break right back out to the first loop?

PhiLho

Re: Nested while loop problem

3 years ago

That's not what I meant by using ifs! It is even uglier this way...

What I meant is: do you really need all these nested loops? Perhaps one loop with proper conditions is better.

Java supports named breaks allowing to jump out of several nested loops, but we rarely need them. Sometime a better algorithm solves the problem more elegantly...

Jack Kern

Re: Nested while loop problem

3 years ago

Another possible method:

boolean done = false;
while( !done )
{  
  if( !a || b || c ) // Inverted logic
    continue;

  while( !done )
  {    
    if (!a || !b || c) // Inverted logic
      continue;

    while( !done )
    {
      // Something changes a/b/c here
      
      if( a && b && c )
      {
        //Do stuff!
        
        done = true; // Break out of all three loops
      }
    }
  }
}

http://www.jackkern.com
http://www.twitter.com/ElectricJack

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