fill in presized lists instead of appending

q15_2.py

def duel(a, b):
    fa = 16807
    fb = 48271
    d = 0x7fffffff
    count1 = 0
    a4 = 5000000*[0]
    b8 = 5000000*[0]
    na = nb = 0
    for i in range(40000000):
        a = (a * fa) % d
        b = (b * fb) % d
        a16 = a & 0xffff
        b16 = b & 0xffff
        count1 += a16 == b16
        if na < 5000000 and not a16 & 0b11:
            a4[na] = a16
            na += 1
        if nb < 5000000 and not b16 & 0b111:
            b8[nb] = b16
            nb += 1
    while nb < 5000000:
        b = (b * fb) % d
        b16 = b & 0xffff
        if not b16 & 0b111:
            b8[nb] = b16
            nb += 1
    count2 = sum(a4[i] == b8[i] for i in range(5000000))
    return count1, count2


assert duel(783, 325) == (650, 336)