gistfile1.txt

# (c) 2023 Aleksei Romanenko, Pterippi Oy
# Licensed under CC BY-SA 4.0

from random import shuffle

def xor_base_n(a, b, n):
    r = ""
    for ai,bi in zip(list(a),list(b)):
        r += str((int(ai) + int(bi)) % n)
    return r

def zeropad(s, l):
    while len(s) < l:
        s = '0' + s
    return s

def rebase(value, base):
    result = ""
    while value:
        value, reminder = divmod(value, base)
        result += str(reminder)
    return result[::-1]

def find_non_repeating_n_times(arr, n): 

    print(sum(arr))
    pad_len = len(rebase(max(arr),n))
    xr = "0" * pad_len
    for i in arr:
        xr = xor_base_n(zeropad(rebase(i, n), pad_len), xr, n)
        print("new value", i, "or", zeropad(rebase(i, n), pad_len), "base", n, " -> accumulated", xr)
    return int(xr, n)


arr = [12, 1, 1, 7, 1, 12, 1]
print("Odd one ", find_non_repeating_n_times(arr, 2))

arr = [12, 1, 1, 5, 1, 12, 12]
print("Odd one ", find_non_repeating_n_times(arr, 3))

arr = [1, 2, 5, 10, 22, 37] * 9 + [42]
shuffle(arr)
print("Odd one ", find_non_repeating_n_times(arr, 9))