Linear Search Algorithm and Implementation in C

Linear Search is basically a sequential search algorithm.

In this algorithm, the key element is searched in the given input array in sequential order.

If the key element is found in the input array, it returns the element.

Linear Search Algorithm

Linear_Search ( Array X, Value i)

• Set j to 1
• If j > n, jump to step 7
• If X[j] == i, jump to step 6
• Then, increment j by 1 i.e. j = j+1
• Go back to step 2
• Display the element i which is found at particular index i, then jump to step 8
• Display element not found in the set of input elements.
• Exit/End

Pseudo Code for Linear Search

procedure LINEAR_SEARCH (array, key)

   for each item in the array
      if match element == key
         return element's index
      end if
   end for

end procedure

Implementation of Linear Search in C

• Initially, we need to mention or accept the element to be searched from the user.
• Then, we create a for loop and start searching for the element in a sequential fashion.
• As soon as the compiler encounters a match i.e. array[element] == key value, return the element along with its position in the array.
• If no values are found that match the input, it returns -1.

#include <stdio.h> 

int LINEAR_SEARCH(int inp_arr[], int size, int val) 
{ 
	 
	for (int i = 0; i < size; i++) 
		if (inp_arr[i] == val) 
			return i; 
	return -1; 
} 


int main(void) 
{ 
	int arr[] = { 10, 20, 30, 40, 50, 100, 0 }; 
	int key = 100; 
	int size = 10; 
	int res = LINEAR_SEARCH(arr, size, key); 
	if (res == -1)
	printf("ELEMENT NOT FOUND!!");
    else
    printf("Item is present at index %d", res);
    
	return 0; 
} 

Output:

Item is present at index 5

Time Complexity of Linear Search

The best-case complexity is O(1) if the element is found in the first iteration of the loop.

The worst-case time complexity is O(n), if the search element is found at the end of the array, provided the size of the array is n.

Conclusion

Thus, in this article, we have understood and implemented Linear Search Algorithm.