C Program to Compare Binary and Sequential Search

This C program compares two searching algorithms – Binary and Sequential Search.

Sequential search is used to find a key in a randomly arranged array. Searching time is O(n). Binary search on the other hand is implemented in a sorted array and is much faster than linear search. Its time complexity is O(log(n)).

Here is the source code of the C program to compare binary and sequential searching algorithms. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
#include <stdio.h>
```
```
#define MAX 10
```

int linearsearch(int numbers[], int key)

```
{
```
```
    int i;
```
```
    for (i = 0; i < MAX; i++)
```
```
    {
```
```
        if (key == numbers[i])
```
```
            return i;
```
```
    }
```
```
    return -1;
```
```
}
```

int binarysearch(int numbers[], int key)

```
{
```
```
    int l = 0, u = MAX - 1;
```
```
    int c, mid;
```
```
     while (l <= u){
```
```
         mid = (l + u) / 2;
```
```
         if (key == numbers[mid]){
```
```
             return mid;
```
```
         }
```
```
         else if (key < numbers[mid]){
```
```
             u = mid - 1;
```
```
         }
```
```
         else
```
```
             l = mid + 1;
```
```
    }
```
```
    return -1;
```
```
}
```
```
int main() {
```
```
    int numbers[MAX];
```
```
    int i;
```
```
    int index, key;
```
```
    printf("Enter %d numbers : ", MAX);
```
```
    for (i = 0; i < MAX; i++)
```
```
    {
```
```
        scanf("%d", &numbers[i]);
```
```
    }
```

    printf("\nEnter a key to find using linear search: ");

```
    scanf("%d", &key);
```
```
    index = linearsearch(numbers, key);
```
```
    if ( index >= 0)
```

        printf("\n%d found at index %d using linear search.", key, index);

```
    else
```
```
        printf("\nNot found!!");
```

    printf("\nEnter %d numbers in increasing order: ", MAX);

```
    for (i = 0 ; i < MAX; i++)
```
```
        scanf("%d", &numbers[i]);
```

    printf("\nEnter a key to find using binary search: ");

```
    scanf("%d", &key);
```
```
    index = binarysearch(numbers, key);
```
```
    if (index >= 0 )
```

        printf("Found at index %d", index);

```
    else
```
```
        printf("\nNot found!!!");
```
```
 
```
```
    return 0;
```
```
    }
```

$ gcc comparesearch.c -o comparesearch
$ ./comparesearch
 
Enter 10 numbers : 1 21 45 66 98 85 78 4 55 48
Enter a key to find using linear search: 45
45 found at index 2 using linear search.
Enter 10 numbers in increasing order: 13 21 45 66 98 99 112 155 185 202 
Enter a key to find using binary search: 66 
Found at index 3

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