Linear search in c

Linear search in c programming: The following code implements linear search (Searching algorithm) which is used to find whether a given number is present in an array and if it is present then at what location it occurs. It is also known as sequential search. It is very simple and works as follows: We keep on comparing each element with the element to search until the desired element is found or list ends. Linear search in c language for multiple occurrences and using function.

Linear search c program

#include <stdio.h>
 
int main()
{
   int array[100], search, c, n;
 
   printf("Enter the number of elements in array\n");
   scanf("%d",&n);
 
   printf("Enter %d integer(s)\n", n);
 
   for (c = 0; c < n; c++)
      scanf("%d", &array[c]);
 
   printf("Enter the number to search\n");
   scanf("%d", &search);
 
   for (c = 0; c < n; c++)
   {
      if (array[c] == search)     /* if required element found */
      {
         printf("%d is present at location %d.\n", search, c+1);
         break;
      }
   }
   if (c == n)
      printf("%d is not present in array.\n", search);
 
   return 0;
}

Output of program:

Linear search for multiple occurrences

In the code below we will print all the locations at which required element is found and also the number of times it occur in the list.

#include <stdio.h>
 
int main()
{
   int array[100], search, c, n, count = 0;
 
   printf("Enter the number of elements in array\n");
   scanf("%d", &n);
 
   printf("Enter %d numbers\n", n);
 
   for ( c = 0 ; c < n ; c++ )
      scanf("%d", &array[c]);
 
   printf("Enter the number to search\n");
   scanf("%d", &search);
 
   for (c = 0; c < n; c++) {
      if (array[c] == search) {
         printf("%d is present at location %d.\n", search, c+1);
  count++;
      }
   }
   if (count == 0)
      printf("%d is not present in array.\n", search);
   else
      printf("%d is present %d times in array.\n", search, count);
 
   return 0;
}

Output of code:

C program for linear search using function

#include <stdio.h>
 
long linear_search(long [], long, long);
 
int main()
{
   long array[100], search, c, n, position;
 
   printf("Input number of elements in array\n");
   scanf("%ld", &n);
 
   printf("Input %d numbers\n", n);
 
   for (c = 0; c < n; c++)
      scanf("%ld", &array[c]);
 
   printf("Input number to search\n");
   scanf("%ld",&search);
 
   position = linear_search(array, n, search);
 
   if (position == -1)
      printf("%d is not present in array.\n", search);
   else
      printf("%d is present at location %d.\n", search, position+1);
 
   return 0;
} 
 
long linear_search(long a[], long n, long find) {
   long c;
 
   for (c = 0 ;c < n ; c++ ) {
      if (a[c] == find)
         return c;
   }
 
   return -1;
}

Linear search function using pointers

long linear_search(long *pointer, long n, long find)
{
   long c;
 
   for (c = 0; c < n; c++) {
      if (*(pointer+c) == find)
         return c;
   }
 
   return -1;
}

Time required to search an element using linear search algorithm depends on size of list. In best case element is present at beginning of list and in worst case element is present at the end. Time complexity of linear search is O(n).