Normally, we decompose a number into binary digits by assigning it with powers of 2, with a coefficient of `0` or `1` for each term:

`25 = 1*16 + 1*8 + 0*4 + 0*2 + 1*1`

The choice of `0` and `1` is... not very binary. We shall perform the *true* binary expansion by expanding with powers of 2, but with a coefficient of `1` or `-1` instead:

`25 = 1*16 + 1*8 + 1*4 - 1*2 - 1*1`

Now *this* looks binary.

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Given any positive number `n`, expand it using the true binary expansion, and return the result as an array, from the most significant digit to the least significant digit.

`true_binary(25) == [1,1,1,-1,-1]`

It should be trivial (the proofs are left as an exercise to the reader) to see that:

- Every odd number has infinitely many true binary expansions
- Every even number has no true binary expansions

Hence, `n` will always be an odd number, and you should return the *least* true binary expansion for any `n`.

Also, note that `n` can be very, very large, so your code should be very efficient.

Difficulty: EASY
Starter code: def true_binary(n):
	

Solutions:
def true_binary(n):
	return [(c == '1') * 2 - 1 for c in '1' + bin(n)[2:-1]]


def true_binary(n):
	return [-1 if x == '0' else 1 for x in bin(n)[1:-1]]


def true_binary(n):
	return [1] + [1 if b == '1' else -1 for b in bin(n)[2:-1]]


def true_binary(n):
	return [1 if d == '1' else -1 for d in (f'1{n >> 1:b}' if n > 1 else '1')]


true_binary = lambda n: [1] + [int(c) * 2 - 1 for c in bin(n)[2:-1]]


import math as m

def true_binary(n):
	c = 1
	c = m.ceil(m.log(n, 2))
	if c == 0:
		c = 1
	n = (n + (2 ** c - 1)) // 2
	return [(char == '1') * 2 - 1 for char in bin(n)[2:]]


def true_binary(n):
	temp = bin(n)[2:]
	return [1 if i == '1' else -1 for i in temp[-1] + temp[:-1]]


def true_binary(n):
	suma = '{:0b}'.format(n)
	ans = [int(suma[0])]
	for i in range(1, len(suma)):
		if suma[i - 1] == '0':
			ans.append(-1)
		else:
			ans.append(1)
	return ans


import re

def true_binary(n):
	s = bin(n)[2:]
	s = re.sub('0+1', lambda x: '1' + '0' * (len(x[0]) - 1), s)
	return [1 if c == '1' else -1 for c in s]