Linear Search in Python (with Source code)

In this post, you will learn what is linear search in python with a detailed explanation and source code.

Linear Search

Linear Search is a searching algorithm in which we sequentially search for a presence of a particular element inside a list or array.

Example:

Algorithm for Linear Search

Suppose we have a list of even numbers such as L1 = [2,4,6,8,10,12] and user want to find element x = 8.

1.	apply while loop on list L1 –> while i < len(l1):
2.	Inside while-loop check if L1[i] == x then print i and break a loop (because you found x at ith position)
3.	Otherwise outside of the while-loop checkif i >= len(L1)then print( 'element is not present inside a list)

Source Code

l1 = [2,4,6,8,10,12]


x = 8   # element that we want to be found
i = 0   # pointer 

while i < len(l1):
    if l1[i] == x:
        print(f'element {x} present at {i}th position')
        break
    i+=1

if i >= len(l1):
    print('Element is not present')

Output

element 8 present at 3th position

Linear Search in python using function

Question: Write a Linear Search program in python using Function

Few concepts of python you should know before writing a program:

1. Function in python &
2. for-loop in python.

Algorithm for Linear Search using function

1.	Define a function –>def Linear_search(L1,x):
2.	apply for-loop on list L1 –> for i in range(len(L1)):
3.	Inside for-loop check if L1[i] == x then return i.
4.	Otherwise outside of the for-loop return -1.

Source code

def LinearSearch(l1, element):
    for i in range(len(l1)):
        if l1[i] == element:
            return i   #return index value
    return -1  # if element is not found then it return -1

list1 = [2,4,6,8,10,12]
x = 8

print(LinearSearch(list1,x))

Output

3

Linear Search in python using using recursion

Question: Write a Linear Search program in python using recursion.

Few concepts of python you should know before writing program:

1. Function in python
2. recursive function in python &
3. for-loop in python.

Algorithm for Linear Search using recursion

1.	Define a function –>def Linear_search(L1,element,pointer): Here pointer initially points to the first element of the list.
2.	if pointer >= len(L1) then return -1
3.	if L1[pointer] == element then return pointer.
4.	Otherwisereturn Linear_search(L1,element,pointer+1).

Source Code

def Linear_search(l1,element,pointer):
    if pointer >= len(l1):
        return -1

    if l1[pointer] == element:
        return pointer
    return Linear_search(l1,element,pointer+1)

list1 = [2,4,6,8,10,12]
x = 8
i = 0  #pointer
print(Linear_search(list1,x,i))

Output

3