Single Number XOR
LeetCode 136 · View on LeetCode
XOR all elements together. Since x ^ x = 0 and x ^ 0 = x, every duplicate cancels out, leaving only the single unique number.
from functools import reduce
from operator import xor
def single_number(nums: list[int]) -> int:
return reduce(xor, nums)
if __name__ == '__main__':
print(single_number([2, 2, 1])) # 1
print(single_number([4, 1, 2, 1, 2])) # 4
print(single_number([1])) # 1