Thread: problem in divide and conquer approach to find max-min

Can you please solve your exercises one by one?

Learn the difference between "==" and "=".

Learn to indent your code when posting it.

Tim S.

The problem is here

Code:

maxmin(0,n-1,max,min);
printf("the maximum element is- %d\n",max);
printf("the minimum element is- %d\n",min);

No matter what your function maxmin does, the calling function retains the original values of max and min. If you want your function to be able to modify the values of max and min, you must call your function like this

Code:

maxmin(0,n-1,&max,&min);
printf("the maximum element is- %d\n",max);
printf("the minimum element is- %d\n",min);

And then define the arguments to maxmin with appropriate pointer types.

Also, I notice you defined max and min as global but you are not using them as global. Better to define them inside your function scope rather than global. Same with your array.

Sorry, but "do it for me" requests are largely going to be ignored here. We're here to help you learn, not to do it for you.

I suggest that you post your updated code where you have applied the advice given so far.

Compile at a high warning level: your compiler should be warning you about something that you need to fix.

There's a great line in a movie "The Lost Boys", where the younger brother's new friend, reveals he's a dedicated teen-age Vampire killer (wanna be), on the hunt to kill a Vampire.

First time he hears this, the older brother turns to his younger brother and asks "Where did you say you met this guy?".

That's my question for this logic here - "Where did you say you thought of this?"

There are two simple ways to get max and min from an array:

1) If the array is being checked AFTER all the values are entered, then:
*assign max and min BOTH to array[0].

*and use two if statements, as you traverse the array in a loop:

Code:

for(each item in the array) {
   if(array[i] > max) max=array[i];
   if(array[i] < min) min = array[i];
}

2) If the array is being checked AS the values are being entered, then:
*assign max and min to the first entered number:

Code:

if(i==0) {
   max=array[0]; 
   min=array[0];
}
//and then continue testing each number, with two if statements, //immediately AFTER the number has been entered into the array:
if(array[i] > max) max=array[i];
if(array[i] < min) min=array[i];

Note that both examples are simple, concise, and require no else or else if statements. Get used to using local variables, unless required to do otherwise.

The younger brother replied, "in the Comic Book store".

And I'm giving out some pseudo code, because this, has been declared a sin against C followers, everywhere:

Code:

    if(i==j) *max=*min=num[i];
    else if(j==(i+1)) {  if(num[i]<num[j]) { *max=num[j]; *min=num[i];}
                         else if(num[i]>num[j]){*max=num[i]; *min=num[j];}
                         else *max=*min=num[i];
                       }
    else
        {
            int mid=(i+j)/2;
            maxmin(i,mid,max,min);
            maxmin(mid+1,j,&max1,&min1);
        }


     if(*max<max1) *max=max1;
     if(*min>min1) *min=min1;
}

Encyclical and Fatwa, to follow.

The values of max1 and min1 are in my opinion undefined/uninitialized most of the time in your code. Therefore I expect a high chance of unpredictable results on some compilers.

Tim S.

Code:

     if(*max<max1) *max=max1;
     if(*min>min1) *min=min1;

But how to increase the warning level of the compiler, presently it shows zero errors and zero warnings.

One would have to know the name of the compiler to know this. Either tell us or do a google search such as

"[Compiler Name] adjust warning level"

I would suggest this as laserlight usually spots these things pretty well, but his answers can be rather cryptic.