linear_search.c

#include<stdio.h>

/* Iterative function to search key in arr[n] */
int linearSearch(int arr[],int n,int k)
{
    int i;
        for(i=0;i<=n;i++) 
        { // iterate n times
            if(arr[i]==k) // if key element matches return the index value
                return i;
        }
    return -1; // return -1 if element not found.
}

/* Recursive function to search key in arr[low...high] */
int recLinearSearch(int arr[], int l, int h, int k)
{
    if (h < l) //if higher index is less than lower index, element not found
        return -1;
    if (arr[l] == k) // if key element matches with array element at lower index
        return l;
    if (arr[h] == k) // if key element matches with array element at higher index
        return h;
    return recLinearSearch(arr, l+1, h-1, k);
}


/* Recursive function to search key in arr[n] */
int recLinearSearch2(int arr[], int n, int k)
{
    if (n < 0) // if index becomes -ve, element not found
        return -1;
    if (arr[n] == k) // if key element matches
        return n;
    return recLinearSearch2(arr, n-1, k);
}

/* main function() */   
int main()
{
    int size,k,i;

    printf("\nEnter no of elements: ");
    scanf("%d",&size);

    int arr[size];

    printf("Enter array elements:");
    for(i=0;i<size;i++)
    scanf("%d",&arr[i]);

    printf("\nEnter the element you want to search : ");
    scanf("%d",&k);
    /* call any one of the following function by un-commenting the line */
    // int index = recLinearSearch(arr, 0, size-1, k);

    // int index = recLinearSearch2(arr, size-1, k);

    int index = linearSearch(arr, size-1, k);

    if (index != -1)
        printf("Element %d is present at index %d", k, index);
    else
        printf("Element %d is not present", k);
    return 0;
}