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Level

IB (Comp Sci)

Topic

04 - b - Algorithms

Linear or Sequential Search

In computer science, linear search or sequential search is a method for finding a target value within a list. It sequentially checks each element of the list for the target value until a match is found or until all the elements have been searched.[1]

Linear search runs in at worst linear time and makes at most n comparisons, where n is the length of the list. If each element is equally likely to be searched, then linear search has an average case of n/2 comparisons, but the average case can be affected if the search probabilities for each element vary. Linear search is rarely practical because other search algorithms and schemes, such as the binary search algorithm and hash tables, allow significantly faster searching for all but short lists

Suggested Video

How to code a Linear search

A step by step implementation of coding a linear search in python

Challenge

#1 Write a Python program to search using the sequential/linear search method

#2 Comment each line of the python solution below to show your understanding of the algorithm

Try it yourself

Solution

def Sequential_Search(dlist, item):

    pos = 0
    found = False
    
    while pos < len(dlist) and not found:
        if dlist[pos] == item:
            found = True
        else:
            pos = pos + 1
    
    return found, pos

print(Sequential_Search([11,23,58,31,56,77,43,12,65,19],31))


Flowchart

Flowchart: Python Data Structures and Algorithms: Sequential search

Visualisations and animations

http://sorting.at/

https://www.hackerearth.com/practice/algorithms/sorting/insertion-sort/visualize/

www.teachyourselfpython.com