Introduction to Linear Search Algorithm: Introduction & Features[With Examples]

What is Searching?

Searching is the process of finding a given element in a list of elements. It helps in the searching of a particular record. Therefore, it is a technique of identifying the place of a given item. The success of a searching process depends on whether the item to be searched has been identified or not.

The Data structure allows the searching of data through two methods.

  1. Linear search or sequential search
  2. Binary search

Linear Search 

Linear search algorithms are a type of algorithm for sequential searching of the data. This algorithm finds a given element with O(n) complexity. It is applied to a collection of items. Each and every item of the data is searched sequentially, and returned if it matches the searched element. If no matches are found, then the search keeps on continuing till the end of the collected data. It is basically a technique of exploring every element while traversing the list. The searching algorithm can be applied to both the sorted and the unsorted data. Practically linear search is rarely used because of the faster searching options provided by other search algorithms like binary search algorithms and hashtables.

Steps in the linear search algorithm

  • Reading of the search element by the user.
  • The element to be searched is compressed with the first element of the list.
  • If the elements match, then a return is generated.
  • If the elements don’t match then the element to be searched is compared to the second element of the list.
  • The process is repeated until the element is matched.

Features of linear search algorithms

  1. It is usually applied to a small list of unsorted or unordered data.
  2. Time is linearly dependent on the number of elements, therefore having a time complexity if O(n).
  3. The implementation is very simple.

Linear search algorithms

A continuous looping method goes on unless and until the item is found

  • algorithm Seqnl_Search(list, item)
  • Pre: list != ;
  • Post: return the index of the item if found, otherwise: 1
  • index <- fi
  • while index < list.Cnt and list[index] != item //cnt: counter variable
  • index <- index + 1
  • end while
  • if index < list.Cnt and list[index] = item
  • return index
  • end if
  • return: 1
  • end Seqnl_Search

Example of linear search 

Problem: Given an array arr[] of n elements, write a function to search a given element x in arr[].

Figure 1: An example of code showing the implementation of linear search algorithm

Source

Linear search algorithms can be used in several programming languages.

  1. Linear search in Python

Figure 2: An example of code showing a linear search algorithm in Python language

Source

Output: Element is present at index 3

  1. Linear search in C

Figure 3: An example of code showing a linear search algorithm in C language

Source

Output: Element is present at index 3

  1. Linear search in Data structure

Pseudocode for a linear search problem in Data structure is 

Figure 4: The pseudocode for linear search algorithm

Source

Binary Search

Binary search is an algorithm to search elements in an array of elements. Compared to the linear search algorithm, the binary search algorithm is applied to a sorted list of data.

Binary search algorithm includes the following steps

  • Comparison of the element to be searched with the element from the middle of the list or array.
  • If the element matches with the element from the list, it returns the index of the middle element.
  • If no match is returned, it is checked whether the element is greater than or lesser than the element in the middle.
  • For an element of greater value than the middle element, the search is carried on the right side of the array.
  • Similarly, if the element is lesser in value than the middle element, then the search is carried on to the left side of the list.

Therefore, binary search is best applied when the data contains large number rod elements in a sorted manner. This makes it a requisite for the search algorithm that the list/array should be sorted.

Features of Binary Search

  • The binary search algorithm is useful for searching a large number of elements in an array.
  • The binary search algorithm has a time complexity of O(logn).
  • Implementation of a binary search algorithm is simple.

Binary Search Algorithm

  • Algorithm Binary_Search(list, item)
  • Set L to 0 and R to n: 1
  • if L > R, then Binary_Search terminates as unsuccessful
  • else
  • Set m (the position in the mid element) to the floor of (L + R) / 2
  • if Am < T, set L to m + 1 and go to step 3
  • if Am > T, set R to m: 1 and go to step 3
  • Now, Am = T,
  • the search is done; return (m)

Example of Binary Search

Figure 5: An example of code showing the implementation of binary search algorithm

Source

Output:

Element is present at index 3

Conclusion

In this article, we have looked into what is a Linear Search Algorithm and also studied in detail how to search for a certain element from a list using the Linear Search Algorithm. Lastly, we also saw how we could practically implement the Linear Search Algorithm using Python 3 as a language and get our desired output.

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