Binary search not returning the position - c

Question

this code is used to create an array filled with 10 random integers. It sorts the array and then inputs the array into a binary search function. I do not get the position of where my search key is positioned.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int binary_search(int array[], int search, int strt, int ending)
{
int middle;
middle = (strt + ending)/2;//splitting the array in half to compare the search key
if (search > array[middle]){binary_search(array, search, middle + 1, ending);}
else if(search == array[middle])
{
printf("Your search key is indicated in %d position the array Ferrari\n", middle + 1);
return middle;
}
else{binary_search(array, search, strt, middle -1);}
return -1;
}
int main()
{
srand(time(NULL));//random number seed generator
int Ferrari[10];
int size = 10;
int selection;
int temporary = 0;//I'm using this variable to store
//the value returned from linear_search()
int start = 0;
int end;
int i;
//this is to generate a random number between 0 and 101
for(int i=0; i<10; i++) {Ferrari[i] = rand() % 100 + 1;}
//printing the initial array
printf("\nThe array Ferrari consists of -> ");
for(int i=0; i<10; i++){printf("%d, ", Ferrari[i]);}
//--------------------------SORTING--------------------------------------------
for(int f = 0; f < (size - 1); f++)
{
for(int kk = 0; kk < (size - 1 - f); kk++)
{
if(Ferrari[kk] > Ferrari[kk +1])
{
int Te_mP;
Te_mP = Ferrari[kk + 1];
Ferrari[kk+1] = Ferrari[kk];
Ferrari[kk] = Te_mP;
}
}
}
//----------------------------------------------------------------------------
//printing the array after it has been sorted
printf("\n");
printf("\nThe sorted array Ferrari consists of -> ");
for(int i=0; i<10; i++){printf("%d, ", Ferrari[i]);}
start = 0;
end = i -1;
//this will be used to implement the searching algorithm
printf("\n\n");
printf("Please enter a number to test if it is included in the array or not\n");
scanf("%d", &selection);
temporary = binary_search(Ferrari, selection, start, end);
return 0;
}
I keep getting the answer that the search key is positioned in ``0 of array Ferrari. How do I resolve this?
Please let me know what I'm doing wrong over here. Much appreciated.

Answer 1

Look at this line
end = i - 1;
Where is i initialized?
In your loop you have
for(int i=0........
Note by giving int i=0 it means you are creating a new variable i within the for block. So this doesn't alter your original i variable declared at the top. Try using end = size - 1 or it's a best practice to define a constant for this purpose.
#define ARR_SIZE 10
in loop
for(i=0; i<ARR_SIZE;i++)
Then initialize end = ARR_SIZE -1;
And one more thing in your binary_search function is that you don't handle the case when the key is not present in the array.
Something like
if(end==start && array[end] != search)
return -1;
This checks when the search space has only one element and that is not your search element, it means it doesn't exist so we return -1.
Hope this helps

Answer 2

The problem is occurring because you are using uninitialised variable i here:
end = i -1;
Note that the scope of variable i declared in loop init clause is different from the scope of variable i declared in function block.
for(int i=0; i<10; i++){
^^^^^^^
// The scope of i declared in loop init clause is limited to the loop.
To fix the problem, you can use the i declared at function block scope as the loop variable, like this
for(i=0; i<10; i++){
Now, after the loop finishes, the variable i will hold its last value until it's value explicitly modify. But using i to identify the size of array down the code may cause several problems as it is not tightly coupled with the size of array and i may be get modified by other part of code. So, it is not the right idea to use i to identify the size of array.
Since, you are having a variable size which hold the size of array Ferrari, you can do:
end = size - 1;
No need to have another variable to keep the track of size of array. The problem with this is that you have to keep updating the size whenever you change the array size. An alternative of this would be to use a macro to define the array size.
The most appropriate way to set the end of array would be:
end = (sizeof(Ferrari) / sizeof(Ferrari[0])) - 1;