Вот мой вариант реализации на С++:
#define SIZE 26
const char low_char[] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
const char high_char[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',
'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
//
// Crypt algorithm
//
std::string crypt(std::string &InputString, int key){
bool OK;
std::string OutputString;
for(unsigned i=0; i
for(int j=0; j
j += key;
while (j >= SIZE) j -= SIZE;
while (j < 0) j += SIZE;
OutputString += low_char[j];
OK=true;
break;
}
if (InputString[i] == high_char[j]) {
j += key;
while (j >= SIZE) j -= SIZE;
while (j < 0) j += SIZE;
OutputString += high_char[j];
OK=true;
break;
}
}
if(!OK)
OutputString +=InputString[i];
}
return OutputString;
}
//
// Decrypt algorithm
//
std::string decrypt(std::string &InputString, int key){
bool OK;
std::string OutputString;
for(unsigned i=0; i
for(int j=0; j
j -= key;
while (j >= SIZE) j -= SIZE;
while (j < 0) j += SIZE;
OutputString += low_char[j];
OK=true;
break;
}
if (InputString[i] == high_char[j]) {
j -= key;
while (j >= SIZE) j -= SIZE;
while (j < 0) j += SIZE;
OutputString += high_char[j];
OK=true;
break;
}
}
if(!OK)
OutputString +=InputString[i];
}
return OutputString;
}