Linear Search

 Linear Search means to traverse a given list or array one by one sequencially starting from the first element with the element to be searched until a match is found or end of the array is reached.

so in the above figure element to be searched is 5 and it is found at index 6.

if the match is found index of the matched element is retured else -1 is returned

Examples :

Input : arr[] = {11,8,34,2,3,76}
          N=6,key = 3;
Output : 4
Element 3 is present at index 4

Input : arr[] = {10, 20, 30, 60, 50, 110, 100}
           N=7,key = 175;
Output : -1
Element 175 is not present in arr[].

implementation:

int search(int arr[], int N, int key) 
{    
     

    // Start traversing the array
    for (int i = 0; i < N; i++) 
    {   
        // If a successful match is found,
        // output the index
        if (arr[i] == key) 
           return i; 
    }

    // If the element is not found,
    // and end of array is reached
    return -1; 
} 

Time Complexity: O(N)

lets implement the same code using cout in c++:

int search(int arr[], int N, int key) 
{    
     
   int p=0;

    // Start traversing the array
    for (int i = 0; i < N; i++) 
    {   
       // if the some array element is equal to element to be searched
        if (arr[i] == key) 
           {
              cout<< i; 
              p++;
              break;
            }
    }
     // if p=0 than element to be searched is found
    // If the element is not found,
    // and end of array is reached
    if(p==1)
    cout<< -1; 
}