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Find the number occurring odd number of times using lambda expression and reduce() function in Python

Learn how to find the number occurring odd number of times using lambda expression and reduce() function in Python?
Submitted by IncludeHelp, on March 14, 2022

Given/input an array of positive integers. We have to find the number which is occurring the odd number of times. All numbers in the list present an even number of times except one (that we have to find).

To find that element – we will use the lambda function and reduce() function. The Lambda function is an anonymous function - that means the function which does not have any name. And, the reduce() function applies to each element of an iterable collection and returns the reduced (based on applied calculation through the function) value.

Example:

Input: 
list1 = [10, 20, 10, 30, 30, 20, 20]

Output:
20

Python code to find the number occurring odd number of times using lambda expression and reduce() function

Define a lambda function and use reduce() function over the list until the single value is left expression reduces the value of x ^ y into single value x starts from 0 and y from 1.

# Importing redecue() function

from functools import reduce

def findElement(list1):
	print (reduce(lambda x, y: x ^ y, list1))

# Main function
if __name__ == "__main__":
	list1 = [10, 20, 10, 30, 30, 20, 20]
	findElement(list1)

Output:

20

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