AOJトライに関する知識知見の記録共有 （Volume0-0040）

概要

Affine Cipher

コード

空白文字に定数-1を割り付け

def char2int(data, inv=False):
    c_seq = "abcdefghijklmnopqrstuvwxyz "
    if inv:
        ret = c_seq[data]
    else:
        ret = -1
        for ret, c in enumerate(c_seq):
            if data == c:
                break
    return ret

def f(c, a, b):
    if c == " ":
        ret = -1
    else:
        ret = (a * char2int(c) + b) % 26
    return ret

def core(enc_str):
    ret = []
    for a_inv in range(1, 26):
        for b in range(26):
            dec_str = "".join([char2int(f(c, a_inv, b), inv=True) for c in enc_str])
            print(dec_str)
            if " that " in dec_str or " this " in dec_str:
                ret.append([[a_inv, b], dec_str])
    return ret

def app(*args):
    return [[arg, core(arg)] for arg in args]

print(app(
"y eazqyp pnop pngtg ye obmpngt xmybp mr lygw",
))

実行結果

デバッグログ出力部含む

[['y eazqyp pnop pngtg ye obmpngt xmybp mr lygw', [[[19, 20], 'i submit that there is another point of view']]]]