Pset3 How do I initialize minimum and maximum in binary search?

Question

I have written the following recursive code for binary search here. The errors I am getting, i think suggests I am not using int min and int max.So the question is how do I initialize or set the values for min and max in the binary search function?

#include <cs50.h>

#include "helpers.h"
bool binarysearch (int values[], int value, int min, int max)
{

    if (min > max)
    {
        return false;
    }    

    int middle = (min + max)/2 ;
    // recursive to go left of the list.
    if (value < values[middle])
    {
        return binarysearch ( values, value, min, middle -1);

    }
    // recursive to go right of the list.
    else if (value > values[middle])
    {
        return binarysearch ( values, value, middle + 1, max);

    }
    else if (value == values[middle])
    {
        return true;
    }

    }

 /**
 * Returns true if value is in array of n values, else false.
 */
bool search(int value, int values[], int n)
{
int min = values[0] ;
int max = values[n - 1];

bool binarysearch (int values[], int value, int min, int max);



}

here is the error that i get when i make find

helpers.c:39:4: error: control may reach end of non-void function
  [-Werror,-Wreturn-type]
   }
   ^
helpers.c:46:8: error: unused variable 'min' [-Werror,-Wunused-variable]
   int min = values[0] ;
   ^
helpers.c:47:8: error: unused variable 'max' [-Werror,-Wunused-variable]
   int max = values[n - 1];
   ^
helpers.c:53:1: error: control reaches end of non-void function
  [-Werror,-Wreturn-type]
   }
   ^ 

Answer 1

I think maybe the issue is with your search() function.

It looks like maybe your line 50 is the issue.

The way you have written this line, it looks like it's a prototype, to be included at the top of a file, to let the compiler know what's coming. Is it possible you were thinking you were calling the function?

Somewhere in the search() function you presumably want to call the binarysearch() function.

You also need to return something in your search() function, since you declared it should have a bool output in line 44.

Since your boolsearch() function also returns a bool, you can probably just return its value, like so:

return binarysearch( values, value, min, max);

I'm thinking maybe you meant that instead of what you have in line 50, but I could be off target.

UPDATE: Change:

 /**
 * Returns true if value is in array of n values, else false.
 */
bool search(int value, int values[], int n)
{
    int min = values[0] ;
    int max = values[n - 1];
    bool binarysearch (int values[], int value, int min, int max);
 }

to:

/**
 * Returns true if value is in array of n values, else false.
 */
bool search(int value, int values[], int n)
{
    int min = values[0] ;
    int max = values[n - 1];
    return binarysearch (values, value, min, max);
 }

That last line of code needs to call the function binarysearch. The way you had it written, it was declaring a prototype of binarysearch.

HTH

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