A Queue implemented with 2 stacks to use for HackerRank problems.

Queue.py

###
# Python 3
# Q = [ [], [] ]
###
def size(Q):
    return len(Q[0]) + len(Q[1])
def is_empty(Q):
    return (len(Q[0]) + len(Q[1])) == 0
def peek(Q):
    if len(Q[1]) == 0:
        while len(Q[0]) > 0:
            Q[1].append(Q[0].pop())
    return Q[1][-1] if len(Q[1]) > 0 else None
def enqueue(Q, x):
    Q[0].append(x)
def dequeue(Q):
    if len(Q[1]) == 0:
        while len(Q[0]) > 0:
            Q[1].append(Q[0].pop())
    return Q[1].pop() if len(Q[1]) > 0 else None
# The End