Linear Search

Linear searching techniques are the simplest technique. In this technique, the items are searched one by one. This procedure is also applicable for unsorted data set. Linear search is also known as sequential search. It is named as linear because its time complexity is of the order of n O(n).

The complexity of Linear Search Technique

• Time Complexity: O(n)
• Space Complexity: O(1)

Input and Output

Input:
A list of data:
20 4 89 75 10 23 45 69
the search key 10
Output:
Item found at location: 4

Algorithm

linearSearch(array, size, key)

Input − An sorted array, size of the array and the search key

Output − location of the key (if found), otherwise wrong location.

Begin
   for i := 0 to size -1 do
      if array[i] = key then
         return i
   done
   return invalid location
End

Example

#include<iostream>
using namespace std;

int linSearch(int array[], int size, int key) {
   for(int i = 0; i<size; i++) {
      if(array[i] == key) //search key in each places of the array
         return i; //location where key is found for the first time
   }
   return -1; //when the key is not in the list
}

int main() {
   int n, searchKey, loc;
   cout << "Enter number of items: ";
   cin >> n;
   int arr[n]; //create an array of size n
   cout << "Enter items: " << endl;

   for(int i = 0; i< n; i++) {
      cin >> arr[i];
   }

   cout << "Enter search key to search in the list: ";
   cin >> searchKey;

   if((loc = linSearch(arr, n, searchKey)) >= 0)
      cout << "Item found at location: " << loc << endl;
   else
      cout << "Item is not found in the list." << endl;
}

Output

Enter number of items: 8
Enter items:
20 4 89 75 10 23 45 69
Enter search key to search in the list: 10
Item found at location: 4