香山杯 [rev] easy_py

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逆向PYC文件：

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def encode(enc, length):
    if length == 0:
        return 0
    for i in range(length):
        enc[length + i] ^= enc[i]
    encode(enc, length >> 1)

tmp = [100, 5, 87, 2, 86, 0, 3, 84, 80, 2, 87, 80, 80, 86, 85, 2, 85, 87, 7, 0, 87, 4, 3, 3, 5, 84, 84, 11, 81, 5, 6, 13]
flag = "?"

if len(flag) != 32:
    exit(0)
enc = map(ord, flag)
encode(enc, len(enc) >> 1)
if tmp == enc:
    print("yes")
else:
    print("wrong")

解密：

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def decode(enc, length):
    if length > 16:
        return 0
    for i in range(length):
        enc[length + i] ^= enc[i]
    decode(enc, length << 1)

今日教训：比赛摸鱼不好好看题，痛失一血= =。