DSA using C - Linear Search

Overview

Linear search is a very simple search algorithm. In this type of search, a sequential search is made over all items one by one. Every items is checked and if a match founds then that particular item is returned otherwise search continues till the end of the data collection.

Algorithm

Linear Search ( A: array of item, n: total no. of items ,x: item to be searched)
Step 1: Set i to 1
Step 2: if i > n then go to step 7
Step 3: if A[i] = x then go to step 6
Step 4: Set i to i + 1
Step 5: Go to Step 2
Step 6: Print Element x Found at index i and go to step 8
Step 7: Print element not found
Step 8: Exit

Example

#include <stdio.h>
#define MAX 20

// array of items on which linear search will be conducted.
int intArray[MAX] = {1,2,3,4,6,7,9,11,12,14,15,16,17,19,33,34,43,45,55,66};

void printline(int count){
   int i;
   for(i=0;i <count-1;i++){
      printf("=");
   }
   printf("=\n");
}
// this method makes a linear search. 
int find(int data){
   int comparisons = 0;
   int index= -1;
   int i;

   // navigate through all items 
   for(i=0;i<MAX;i++){
      // count the comparisons made 
      comparisons++;
      
      // if data found, break the loop 
      if(data == intArray[i]){
         index = i;
         break;
      }
   }
   printf("Total comparisons made: %d", comparisons);
   return index;
}
void display(){
   int i;
   printf("[");
   
   // navigate through all items 
   for(i=0;i<MAX;i++){
      printf("%d ",intArray[i]);
   }
   printf("]\n");
}
main(){
   printf("Input Array: ");
   display();
   printline(50);
   
   //find location of 1
   int location = find(55);

   // if element was found 
   if(location != -1)
      printf("\nElement found at location: %d" ,(location+1));
   else
      printf("Element not found.");
}

Output

If we compile and run the above program then it would produce following output −

Input Array: [1 2 3 4 6 7 9 11 12 14 15 16 17 19 33 34 43 45 55 66 ]
==================================================
Total comparisons made: 19
Element found at location: 19