P2146 [NSSCTF 2022 Spring Recruit]easy Python

直接在线解密TlNTQ1RGe2Jhc2U2NCEhfQ
flag NSSCTF{base64!!

import string  
  
def encode(string,string2):  
    tmp_str = str()  
    ret = str()  
    bit_string_str = string.encode()  
    remain = len( string ) % 3  
    remain_str = str()  
    for char in bit_string_str:  
        b_char = (bin(char)[2:])  
        b_char = '0'*(8-len(b_char)) + b_char  
        tmp_str += b_char  
    for i in range(len(tmp_str)//6):  
        temp_nub = int(tmp_str[i*6:6*(i+1)],2)  
        ret += string2[temp_nub]  
    if remain==2:  
        remain_str = tmp_str[-4:] + '0'*2  
        temp_nub = int(remain_str,2)  
        ret += string2[temp_nub] + "="  
    elif remain==1:  
        remain_str = tmp_str[-2:] + '0'*4  
        temp_nub = int(remain_str,2)  
        ret += string2[temp_nub] + "="*2  
    return ret.replace("=","")  
  
res = encode(input(),string.ascii_uppercase+string.ascii_lowercase+string.digits+'+/')  
  
if res == "TlNTQ1RGe2Jhc2U2NCEhfQ":  
    print("good!")  
else:  
    print("bad!")
​
            
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