Thread: Newb question .. While loop and use of curly brackets on last else in loop

Hi All,

I'm am new to C and was working on a binary search algorithm.

The last else in the while loop has a statement wrapped in curly brackets and it compiles without errors given. But when i run the code it enters an infinite loop. When i remove the curly brackets it gives no errors and runs fine. I don't understand why it gets stuck in an infinite loop. Why is that? Any C experts maybe wanna explain more about this please?

This is the piece of code:

Code:

bool search(int value, int values[], int n)
{
    int first = 0;
    int last = n - 1;
    int middle = ( first + last ) / 2;
    
    while ( first <= last )
    {
        if ( values[middle] == value )
        {
            return true;
        }
        else if ( values[middle] < value )
        {
            first = middle + 1;
        }
        else
        {
            last = middle - 1;
            middle = ( first + last ) / 2;
        } // when removing these bolded brackets the code runs fine
    } 
    return false;
}

And for those interested in the piece of sorting code the above algorithm is merged with:

Code:

void sort(int values[], int n)
{
       for ( int j = 0; j < n - i - 1; j++)
       {
           if ( values[j] > values[j+1] )
           {
               int swap     = values[j];
               values[j]    = values[j+1];
               values[j+1]  = swap;
           }
       }
   }
    return;
}

Originally Posted by Salem

Well without explicit braces, what you have is

Code:

        else
        {
            last = middle - 1;
        }

        // this happens EVERY time, regardless of if / else logic
        middle = ( first + last ) / 2;

Nice. I see now that's what kept it running.

As for the curly brackets, would you say that the "last = middle - 1;" statement should be in brackets no matter what, even if it does run good without 'm?