# Program to find which element occurs exactly once in Python

PythonServer Side ProgrammingProgramming

Suppose we have a list of numbers called nums where each value occurs exactly three times except one value that occurs once. We have to find the unique value. We have to solve it in constant space.

So, if the input is like nums = [3, 3, 3, 8, 4, 4, 4], then the output will be 8

To solve this, we will follow these steps −

• m := a map with different values and their frequencies

• return the value with minimum frequency

Let us see the following implementation to get better understanding −

## Example

Live Demo

from collections import Counter
class Solution:
def solve(self, nums):
nums = Counter(nums)
return min(nums, key=nums.get)
ob = Solution()
nums = [3, 3, 3, 8, 4, 4, 4]
print(ob.solve(nums))

## Input

[3, 3, 3, 8, 4, 4, 4]

## Output

8
Updated on 10-Oct-2020 11:41:12