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Linear Search in C language


Before writing the algorithm or program for searching , let us see, “ What is searching? What are the searching techniques?”
Definition : More often we will be working with the large amount of data. It may be necessary to determine whether a particular item is present in the large amount of data or not. This process of finding a particular item in the large amount of data is called searching. The two important and simple searching techniques are linear search and binary search.

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Linear search (Sequential search)
“What is the linear search?”
Definition: Linear search is a simple searching techniques in which we search for a given key item in the list in linear order(Sequential order) i.e. one after the other. The item to be searched is often called key item. The linear search is also called sequential search.

For example , if key=10 and the list is 20,10,40,25 after searching we say that key is present . If key =100 after searching we say that key is not present.
“How to search for an item in a list of elements?” The procedure is as follows.

Linear/Sequencial Search in C

Procedure: Assume 10 is the item to be searched in the list of items 50,40,30,60,10. Observe from above figure that, 10 has to be compared with a[0], a[1], a[2], a[3], a[4].
But, once the value of I is greater than or equal to 5, it is an indication that item is not present and display the message “Unsuccessful Search”.

Note: In general the terminal condition in the for loop i<5 can be replaced by i<n.
You are already familiar with the algorithm and flowchart of linear search . Now, the C program for linear search is shown below:

int i,n,key,a[20];
printf("Enter the value of n.");
printf("Enter n values:\n");
printf("Enter item to search:");
/* Search the key in array */
printf("item found");
printf("Not found");

Linear Search in C

Linear Search in C

Advantage of linear search

  • Very simple approach
  • Works well for small array
  • Used to search when the elements are not sorted (not in any order)
Disadvantage of linear search

  • Less efficient if the array size is large
  • If the elements are already sorted, linear search is not efficient.

Note : When the elements are not sorted and size is very less, linear search is used . if the elements are sorted , a better method or technique binary search can be used.

Binary Search in C
Selection Search in C


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Difference between Linear search and Binary Search in c language

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Binary Search Linear Search Works only on sorted items. such as  1,2,3,4,5,6  etc
Works on sorted as well as unsorted items. 12,4,5,3,2,1 etc Very efficient if the items are sorted Very efficient if the items are less and present in the beginning of the list. such as Suppose your list items are : 12,3,4,5,1 and you want to search 12 number then you get beginning in the list. Works well with arrays and not on linked lists. Works with arrays and linked lists.
Number of comparisons are less More number of comparisons are required if the items are present in the later part of the array or its elements are more.

Memory representation of Linked List Data Structures in C Language

Memory representation of Linked List

             In memory the linked list is stored in scattered cells (locations).The memory for each node is allocated dynamically means as and when required. So the Linked List can increase as per the user wish and the size is not fixed, it can vary.

               Suppose first node of linked list is allocated with an address 1008. Its graphical representation looks like the figure shown below:

      Suppose next node is allocated at an address 506, so the list becomes,

  Suppose next node is allocated with an address with an address 10,s the list become,

The other way to represent the linked list is as shown below:

 In the above representation the data stored in the linked list is “INDIA”, the information part of each node contains one character. The external pointer root points to first node’s address 1005. The link part of the node containing information I contains 1007, the address of next node. The last node …