How to convert a decimal base (10) to a negabinary base (-2)?
def neg2dec(arr):
n = 0
for i, num in enumerate(arr[::-1]):
n+= ((-2)**i)*num
return n
def dec2neg(num):
if num == 0:
digits = ['0']
else:
digits = []
while num != 0:
num, remainder = divmod(num, -2)
if remainder < 0:
num, remainder = num + 1, remainder + 2
digits.append(str(remainder))
return ''.join(digits[::-1])
The algorithm is described in http://en.wikipedia.org/wiki/Negative_base#Calculation. Basically, you just pick the remainder as the positive base case and make sure the remainder is nonnegative and minimal.
7 = -3*-2 + 1 (least significant digit)
-3 = 2*-2 + 1
2 = -1*-2 + 0
-1 = 1*-2 + 1
1 = 0*-2 + 1 (most significant digit)