I was implementing binary search in C and I'm facing this problem which is that its not printing the index number of the element

Question

Function For Binary Search

#include <stdio.h>
int binarySearch(int arr[], int size, int element, int low, int high)
{
    int mid;
    while (low <= high)
    {
        if (arr[mid] == element)
        {
            return mid;
        }
        if (element < arr[mid]) //element is on the left side
        {
            high = mid - 1;
        }
        else
        {
            low = mid + 1; //element is on the right side
        }
    }
    return -1;
}

Main Program Starts Here

int main()
{

    int arr[] = {1, 5, 10, 16, 24, 30, 50, 100};
    int size = sizeof(arr) / sizeof(int);
    int element = 10;
    int low = 0;
    int high = size - 1;
    int search = binarySearch(arr, size, element, low, high);

so, my problem is that it's not printing this line and in the first place, the compiler is not executing the program. Whenever I try to execute it my pc gets hang

    printf("The element %d was found at index %d", element, search);
    return 0;
}

Answer 1

Your problem is that you forgot to declare initializes/defines mid, which will lead to undefined behavior (after that, anything can happened to your program). You'll also need to recalculate mid every time the loop runs.

Also, as @DavidC.Rankin mentioned below, your sizeArr parameter is quite unnecessary.

Modified code:

#include <stdio.h>
int binarySearch(int arr[], int element, int low, int high)
{
    int mid; //declare here

    while (low <= high)
    {
        mid = (low+high)/2; //recalculate here
        if (arr[mid] == element)
        {
            return mid;
        }
        else if (element < arr[mid]) //element is on the left side
        {
            high = mid - 1;
        }
        else
        {
            low = mid + 1; //element is on the right side
        }
    }
    return -1;
}

int main()
{
    int arr[] = {1, 5, 10, 16, 24, 30, 50, 100};
    int sizeArr = sizeof(arr) / sizeof(int);
    int element = 10;
    int low = 0;
    int high = sizeArr - 1;
    int searchResult = binarySearch(arr, sizeArr, element, low, high);
    printf("The element %d was found at index %d", element, searchResult);
    return 0;
}

Result : The element 10 was found at index 2

Noted that keywords such as search or size shouldn't be used as variable names.