Linear Search is the simplest searching algorithm that checks each element sequentially until a match is found. It is good for unsorted arrays and small datasets.

Given an array a[] of n elements, write a function to search for a given element x in a[] and return the index of the element where it is present. If the element is not present in the array, then return -1.

Input/Output:

Input: a = [ 1, 2, 3, 5, 7], x = 3
Output = Element found at index: 2

Input a = [1, 2, 3, 5, 7] x = 8
Output = -1

Try it on GfG Practice

Algorithm for Linear Search

• Start 
• Declare an array and search element as the key.
• Traverse the array until the number is found.
• If the key element is found, return the index position of the array element
• If the key element is not found, return -1
• Stop.

Please refer to the complete article on Linear Search for more details.

Linear Search in Java

Example:

// Java code for linearly search x in arr[]. If x
// is present then return its location, otherwise
// return -1
class Geeks
{

  	static int search(int a[], int n, int x)
    {
        for (int i = 0; i < n; i++) {
            if (a[i] == x)
                return i;
        }

        // return -1 if the element is not found
        return -1;
    }

    public static void main(String[] args)
    {
        int[] a = { 3, 4, 1, 7, 5 };
        int n = a.length;
        
        int x = 4;

        int index = search(a, n, x);
        
      	if (index == -1)
            System.out.println("Element is not present in the array");
        else
            System.out.println("Element found at index: " + index);
    }
}

// Java code for linearly search x in arr[]. If x

// is present then return its location, otherwise

// return -1

class Geeks

{

​

    static int search(int a[], int n, int x)

    {

        for (int i = 0; i < n; i++) {

            if (a[i] == x)

                return i;

        }

​

        // return -1 if the element is not found

        return -1;

    }

​

    public static void main(String[] args)

    {

        int[] a = { 3, 4, 1, 7, 5 };

        int n = a.length;

        int x = 4;

​

        int index = search(a, n, x);

        if (index == -1)

            System.out.println("Element is not present in the array");

        else

            System.out.println("Element found at index: " + index);

    }

}

Element found at position 1

Time Complexity:

• Best Case Complexity: The best-case time complexity of the linear search is O(1).
• Average Case Complexity: The average case time complexity of the linear search is O(n).
• Worst-Case Complexity: The worst-case time complexity of the linear search is O(n).

Space Complexity: O(1)