IterativeBinarySearch.c

// C program to implement Binary Search using Iterative Approach i.e Using Loop
#include <stdio.h>

/*(l is leftmost index , r the rightmost index and val is the element we are
   searching for) If value is present return the index else return -1
    */
int binarySearch(int arr[], int l, int r, int val) {
  int mid = 0;
  while (l <= r) {
    // Storing the middle index of the array
    mid = (l + r) / 2;
    // value matched with X i.e searched element
    if (arr[mid] == val) {
      return mid;
    }
    /* If val is less than the mid element
            Check the left sub-array */
    else if (val < arr[mid]) {
      r = mid - 1;
    }
    /* If val is greater than the mid element
    Check the right sub-array */
    else {
      l = mid + 1;
    }
  }
  /* value not found in the array
  return with -1 response */
  return -1;
}

int main() {
  int arr[] = {-2, 5, 14, 17, 19, 27};
  // searched value assuming to be val=19
  int val = 19;
  int n = sizeof(arr) / sizeof(arr[0]);
  int index = binarySearch(arr, 0, n - 1, val);

  if (index == -1) {
    printf("\nThe element %d is not present in the array", val);
  } else {
    printf("\nThe element %d is present at index: %d", val, index);
  }
  return 0;
}

// Time Complexity: O(logn)
// Space Complexity: O(n)

/* Sample Test Case:
Test-1:
        IF searched value is 19
        i.e val=19
        ------
        Output
        ------
        The element 19 is not present at index: 4

Test-2:
        IF searched value is 29
        i.e val=29
        ------
        Output
        ------
        The element 29 is not present in the array
 */