C Binary & Linear Search

Question

Hello i want to draw the time/array size graph for binary and linear search algorithms.(Worst, best and average case for array size = 1 000, 10 000,100 000,1 000 000). I'm using DEV C++. However, when i run the code for array size = 1 000 000, the program crashes. Here is the code :

#include <stdio.h>

int binarySearch(int arr[], int l, int r, int x)
{
   if (r >= l)
   {
        int mid = l + (r - l)/2;

        if (arr[mid] == x)  return mid;

        if (arr[mid] > x) return binarySearch(arr, l, mid-1, x);

        return binarySearch(arr, mid+1, r, x);
   }

   return -1;
}

int main(void)
{
   int arr[10] = {2,5,8,9,15,18,19,25,34,50};
   int n = sizeof(arr)/ sizeof(arr[0]);
   int x = 10;
   int result = binarySearch(arr, 0, n-1, x);
   (result == -1)? printf("Element is not present in array")
                 : printf("Element is present at index %d", result);
   return 0;
}

Try using dynamically allocated arrays instead of statically allocated ones. — J...S, Oct 08 '17 at 12:58
If `x` is not in the array, your `binarySearch()` will be infinitely recursive, since the only way the function returns without a doing recursive call is if `arr[mid] == x`. The value`10` is not in the array, hence the crash. — Peter, Oct 08 '17 at 14:20

Daniel Sęk · Answer 1 · 2017-10-08T14:30:07.100

2

You are allocating array arr on stack. For 1 000 000 elements you need 4 MB of memory (assuming that sizeof(int) == 4). On Windows for example most of cases stack has default limit of 1 MB. For quick fix define arr as static

static int arr[size];

or put in global scope outside function body or as others said, use dynamic allocation.

edited Oct 08 '17 at 14:30

answered Oct 08 '17 at 13:52

Daniel Sęk

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He could use the heap instead, as you suggested in your Edit :) – Grantly Oct 08 '17 at 14:13

C Binary & Linear Search

1 Answers1