 # Python Program to Find Sum of Odd Numbers Using Recursion in a List/Array

In the previous article, we have discussed Python Program to Check Armstrong Number using Recursion

Given a list and the task is to find the sum of odd numbers using recursion in a given list in python.

Recursion:

Recursion is the process by which a function calls itself directly or indirectly, and the associated function is known as a recursive function. Certain issues can be addressed fairly easily using a recursive approach. Towers of Hanoi (TOH), Inorder /Preorder/Postorder Tree Traversals, DFS of Graph, and other analogous issues are examples.

Examples:

Example1:

Input:

Given List = [6, 12, 4, 2, 3, 9, 1, 5]

Output:

The Sum of Odd Elements in a given list [6, 12, 4, 2, 3, 9, 1, 5] = 18

Example2:

Input:

Given List = [4, 3, 1, 5, 11]

Output:

The Sum of Odd Elements in a given list [4, 3, 1, 5, 11] = 20

## Program to Find Sum of Odd Numbers Using Recursion in a List/Array in Python

Below are the ways to find the sum of odd numbers using recursion in a given list in python:

### Method #1: Using Recursion (Static Input)

Approach:

• Give the list as static input and store it in a variable.
• Calculate the length of the given list and store it in another variable.
• Take a variable say rslt_sum and initialize its value to 0.
• Pass the given list and length of the given list as the arguments to the oddelemt_sum function.
• Create a recursive function to say oddelemt_sum which takes the given list and length of the given list as the arguments and returns the sum of odd numbers in a given list using recursion.
• Make the rslt_sum a global declaration.
• Check if the length of the given list is greater than 0 using the if conditional statement.
• If the statement is true, then subtract 1 from the length of the given list and store it in a variable k.
• Check if the element present at the index k of the given list is odd using the modulus operator and if conditional statement.
• If the statement is true, add the element present at the index k of the given list to the above-initialized rslt_sum.
• Store it in the same variable.
• Pass the given list and k value as the arguments to the oddelemt_sum function.{Recursive Logic}
• Return rslt_sum.
• Print the sum of odd numbers in the above-given list.
• The Exit of the Program.

Below is the implementation:

# Create a recursive function to say oddelemt_sum which takes the given list and length
# of the given list as the arguments and returns the sum of odd numbers in a given list
# using recursion.

def oddelemt_sum(gven_lst, len_lst):
# Make the rslt_sum a global declaration.
global rslt_sum
# Check if the length of the given list is greater than 0 using the if conditional
# statement.
if(len_lst > 0):
# If the statement is true, then subtract 1 from the length of the given list and
# store it in a variable k.
k = len_lst-1
# Check if the element present at the index k of the given list is odd using modulus
# operator and if conditional statement.
if(gven_lst[k] % 2 != 0):
# If the statement is true, add the element present at the index k of the
# given list to the above-initialized rslt_sum.
# Store it in the same variable.
rslt_sum = rslt_sum+gven_lst[k]
# Pass the given list and k value as the arguments to the oddelemt_sum function
# {Recursive Logic}.
oddelemt_sum(gven_lst, k)
# Return rslt_sum.
return rslt_sum

# Give the list as static input and store it in a variable.
gven_lst = [6, 12, 4, 2, 3, 9, 1, 5]
# Calculate the length of the given list and store it in another variable.
len_lst = len(gven_lst)
# Take a variable say rslt_sum and initialize its value to 0.
rslt_sum = 0
# Pass the given list and length of the given list as the arguments to the oddelemt_sum
# function.
# Print the sum of odd numbers in the above-given list.
print("The Sum of Odd Elements in a given list",
gven_lst, "=", oddelemt_sum(gven_lst, len_lst))


Output:

The Sum of Odd Elements in a given list [6, 12, 4, 2, 3, 9, 1, 5] = 18

### Method #2: Using Recursion (User Input)

Approach:

• Give the list as user input using list(),map(),input(),and split() functions.
• Store it in a variable.
• Calculate the length of the given list and store it in another variable.
• Take a variable say rslt_sum and initialize its value to 0.
• Pass the given list and length of the given list as the arguments to the oddelemt_sum function.
• Create a recursive function to say oddelemt_sum which takes the given list and length of the given list as the arguments and returns the sum of odd numbers in a given list using recursion.
• Make the rslt_sum a global declaration.
• Check if the length of the given list is greater than 0 using the if conditional statement.
• If the statement is true, then subtract 1 from the length of the given list and store it in a variable k.
• Check if the element present at the index k of the given list is odd using the modulus operator and if conditional statement.
• If the statement is true, add the element present at the index k of the given list to the above-initialized rslt_sum.
• Store it in the same variable.
• Pass the given list and k value as the arguments to the oddelemt_sum function.{Recursive Logic}
• Return rslt_sum.
• Print the sum of odd numbers in the above-given list.
• The Exit of the Program.

Below is the implementation:

# Create a recursive function to say oddelemt_sum which takes the given list and length
# of the given list as the arguments and returns the sum of odd numbers in a given list
# using recursion.

def oddelemt_sum(gven_lst, len_lst):
# Make the rslt_sum a global declaration.
global rslt_sum
# Check if the length of the given list is greater than 0 using the if conditional
# statement.
if(len_lst > 0):
# If the statement is true, then subtract 1 from the length of the given list and
# store it in a variable k.
k = len_lst-1
# Check if the element present at the index k of the given list is odd using modulus
# operator and if conditional statement.
if(gven_lst[k] % 2 != 0):
# If the statement is true, add the element present at the index k of the
# given list to the above-initialized rslt_sum.
# Store it in the same variable.
rslt_sum = rslt_sum+gven_lst[k]
# Pass the given list and k value as the arguments to the oddelemt_sum function
# {Recursive Logic}.
oddelemt_sum(gven_lst, k)
# Return rslt_sum.
return rslt_sum

# Give the list as user input using list(),map(),input(),and split() functions.
# Store it in a variable.
gven_lst = list(map(int, input(
'Enter some random List Elements separated by spaces = ').split()))
# Calculate the length of the given list and store it in another variable.
len_lst = len(gven_lst)
# Take a variable say rslt_sum and initialize its value to 0.
rslt_sum = 0
# Pass the given list and length of the given list as the arguments to the oddelemt_sum
# function.
# Print the sum of odd numbers in the above-given list.
print("The Sum of Odd Elements in a given list",
gven_lst, "=", oddelemt_sum(gven_lst, len_lst))


Output:

Enter some random List Elements separated by spaces = 4 3 1 5 11
The Sum of Odd Elements in a given list [4, 3, 1, 5, 11] = 20

Find the best practical and ready-to-use Python Programming Examples that you can simply run on a variety of platforms and never stop learning.