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Algorithms & data structures easy

Find Single Number Appearing Once in Python

Count frequency of each number in a list and return the one that appears exactly once when all others appear twice.

counter frequency single-number
Python 
from collections import Counter

def find_single_number(nums):
    counts = Counter(nums)
    for num, count in counts.items():
        if count == 1:
            return num
    return None

if __name__ == "__main__":
    nums = [4, 1, 2, 1, 2]
    result = find_single_number(nums)
    print(f"Single number in {nums} …
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