Convolutional Encode Stream

Problem

Encode a whole bit stream with a rate-1/2 convolutional encoder. The state list holds the previous input bits, and for each new bit form combined = [bit] + state; each output parity is the XOR of the combined bits named by its tap list, after which the state shifts in the new bit. Return the flat interleaved stream [p1, p2, p1, p2, ...].

Hint

Tap index 0 is the current bit, so a tap list of [0] just copies the input to that output.

Test cases

case 1

in: [[1,0,1],[0,0],[0,1,2],[0,2]]

expected: [1,1,1,0,0,0]

case 2

in: [[1,1],[0,0],[0,1],[0,1,2]]

expected: [1,1,0,0]

case 3

in: [[],[0,0],[0,1],[0,1,2]]

expected: []

case 4

in: [[1,0,0,1],[0],[0,1],[0]]

expected: [1,1,1,0,0,0,1,1]

Starter codePython

def convolutional_encode(bits, state, taps1, taps2):
    # Your code here
    pass

4 test cases · run your code against them in the editor