CodePudding user response:

CodePudding user response:

 cin> K> C;//enter key, ciphertext 
for (int i=0; i{
Int t=(k [I % Kuala Lumpur ength ()] & amp; 31) - 1;//ciphertext corresponds to the current position of the key characters, namely ciphertext [I] the c I position corresponding to the key position, I 
//because cipher (clear) may be longer than the key, and known key can be recycled, so after I location beyond the length of the k and starting from zero position, 
//so I % Kuala Lumpur ength () 
//as for & amp; 31 processing, actually and % 32 processing are equivalent (why their equivalence in binary, don't dwell on here), 
//and lowercase letters are just 32, namely the 'a' and 'a' ASCII just 32 difference, so the result of the % 32 lowercase letters are the same as 
//and [I] % 32 k just to get the position of the corresponding characters, 
//such as' a '% 32=1 (' a' % 32=1), which is equivalent to get letters a corresponding position (position starting from 0, so 1) 
[I]=c (c [I] & amp; 31) - t> 0? C - t: [I] [I] - t + c; [I]//c % 32 is the same as the above said c [I] the characters corresponding to the location of the position - [I] t is calculated and k of relative distance 
//if relative distance is greater than 0 c [I] - t for plaintext characters (plaintext: line + keys: column=cipher, which in turn is clear=ciphertext - key) 
//is like case ciphertext 'H' % 32 - (key 'a' % 32-1)=clear 'H') 
//if the distance is less than zero, the result plus 26 rounds a circle back (the equivalent of letters) 
} 
Cout