Linear search in c | Algorithm of Linear search | c programming

A linear search algorithm is a sequential search algorithm that start at one end of a list and search through each element until the desired element is found, otherwise the search continues to the end of the list. It is the simplest algorithm for search.

Implementing a linear search is simple

• One by one, compare key with each element of array.
• Return the index if key matches an element.
• The return value will be -1 if key does not match any of the element.

Linear Search c program

#include<stdio.h>
    
    int main(){
    
        int n;
        printf("Enter the size of array : ");
        scanf("%d", &n);
    
        int arr[n];
    
        printf("\nEnter the element in array : ");
        for(int i=0; i<n; i++){
            scanf("%d", &arr[i]);
        }
    
    
        // searching
        int isFound = 0;
        int key;
        printf("\nEnter the key do you want to searh the element : ");
        scanf("%d", &key);
        for(int i=0; i<n; i++){
            if(arr[i]==key){
                isFound = 1;
                break;
            }
        }
    
        if(isFound==1){
            printf("Element present in array ");
        }
        else{
            printf("Element is not present in array ");
        }
        return 0;
    }
    
    /*
    
    Enter the size of array : 5
    
    Enter the element in array : 4 9 2 8 7
    
    Enter the key do you want to searh the element : 8
    Element present in array 
    
    */

Recursive Linear search in c

• In the case of a Zero-sized array, return -1, which indicates that an element has not been found.
• Check if the current element in the array matches the key be comparing arr[size-1] with key.
• Return the key index if equal.

#include<stdio.h>
    #include<stdbool.h>
    
    bool linearSearchRecursive(int arr[], int size, int key){
         // if size of array is zero
        if(size == 0){
            return false;
        }else if(arr[size - 1] == key){
            // if the key is present in the last of the array
            return true;
        }else{
            return linearSearchRecursive(arr, size - 1, key);
        }
    }
    
    int main(){
    
        int n;
        printf("Enter the size of array : ");
        scanf("%d", &n);
    
        int arr[n];
    
        printf("\nEnter the element in array : ");
        for(int i=0; i<n; i++){
            scanf("%d", &arr[i]);
        }
    
    
        // searching
        bool isFound;
        int key;
        printf("\nEnter the key do you want to searh the element : ");
        scanf("%d", &key);
    
        isFound = linearSearchRecursive(arr, n, key);
    
        if(isFound){
            printf("Element present in array ");
        }
        else{
            printf("Element is not present in array ");
        }
        return 0;
    }
    
    /*
    
    Enter the size of array : 5
    
    Enter the element in array : 7 8 1 2 3
    
    Enter the key do you want to searh the element : 3
    Element present in array 
    
    */

Time complexity of linear search

Space Complexity of Linear search

The space complexity of linear search is O(1).