Witch From Mercury DNA Cipher Encode/Decode C++ Implementation

README.md

Witch From Mercury DNA Cipher Encode/Decode C++ Implementation

Simple Explanation of the DNA Cipher

1. Each character is expressed by a 3-letter codon.
2. Each codon is expressed by a 3-digit number in base 4. A is 0, C is 1, G is 2, T is 3.
   • Example: ACG = 0*4^2 + 1*4^1 + 2*4^0 = 6, which represents the 7th letter of the alphabet, G. (since we start from 0)
3. Lower case letters are expressed by the numbers 0-25, upper case letters are expressed by the numbers 37-62. So lower case start with AAA and upper case start with GCC.
4. The numbers 26-30 represent the characters ' ', '.', ',', '!', and '?' respectively.
5. The numbers 31-36 are not used, so are numbers greater than 62.

Usage

Simply compile the program using GCC and run it. It will prompt you for a message to encode or decode, and then it will print the result.

Example

Take this screenshot from the anime as an example: It should produce the following result:

Enter 'encode' or 'decode': decode
Enter DNA code: GTCCGGCCGAGAAGTAGTCGGAAAAGTCCGAAACGAC
Message: I will alway
Would you like to encode/decode another message? (y/n): y

Enter 'encode' or 'decode': decode
Enter DNA code: GTAATGCCGCGGAAACACACACGGATGCCACACCGGCATATGATAAAACATATGACACAGCTG
Message: How are our tomatoes?
Would you like to encode/decode another message? (y/n): y

Enter 'encode' or 'decode': encode
Enter message: How are our tomatoes?
DNA code: GTAATGCCGCGGAAACACACACGGATGCCACACCGGCATATGATAAAACATATGACACAGCTG
Would you like to encode/decode another message? (y/n): n

Credits

• Credit by: @rune2304 in YouTube comment
• Link to the post

main.cpp

#include <iostream>
#include <cmath>

void validateDNA(std::string& s);
void validateMSG(std::string& s);
void decode(std::string& s);
void encode(std::string& s);

int main() {
    do{
        std::string mode = "";
        do{
            std::cout << "Enter 'encode' or 'decode': ";
            std::cin >> mode;
            if(mode != "encode" && mode != "decode"){
                std::cout << "Invalid mode. Please try again." << std::endl;
                mode.clear();
            }
        }while(mode.empty());
        std::cin.ignore();
        if(mode == "encode"){
            std::string msg = "";
            do{
                std::cout << "Enter message: ";
                std::getline(std::cin, msg);
                validateMSG(msg);
                if(msg.empty()){
                    std::cout << "Invalid message. Please try again." << std::endl;
                }
            }while(msg.empty());
            encode(msg);
        }
        else if(mode == "decode"){
            std::string code = "";
            do{
                std::cout << "Enter DNA code: ";
                std::cin >> code;
                validateDNA(code);
                if(code.empty()){
                    std::cout << "Invalid code. Please try again." << std::endl;
                }
            }while(code.empty());
            decode(code);
        }
        std::cout << "Would you like to encode/decode another message? (y/n): ";
        char c;
        std::cin >> c;
        if(c == 'n'){
            break;
        }
        std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
        std::cout << std::endl;
    }while(true);
    
}

void decode(std::string& s){
    std::string codon = "";
    std::string message = "";
    for(size_t i = 0; i < s.length(); i+=3){
        unsigned val = 0;
        codon = s.substr(i, 3);
        for(size_t j = 0; j < codon.length(); j++){
            switch(codon[j]){
                case 'A':
                    val += 0;
                    break;
                case 'C':
                    val += 1 * pow(4, 2-j);
                    break;
                case 'G':
                    val += 2 * pow(4, 2-j);
                    break;
                case 'T':
                    val += 3 * pow(4, 2-j);
                    break;
            }
        }
        if(val > 36 && val < 63){
            message += 'A' + val - 37;
        }
        else if(val < 26){
            message += 'a' + val;
        }
        else if(val >= 26 && val < 31){
            switch(val){
                case 26:
                    message += ' ';
                    break;
                case 27:
                    message += '.';
                    break;
                case 28:
                    message += ',';
                    break;
                case 29:
                    message += '!';
                    break;
                case 30:
                    message += '?';
                    break;
            }
        }
        else{
            std::cout << "Invalid DNA codon: " << codon << ". Replacing with '*'." << std::endl;
            message += '*';
        }
    }
    std::cout << "Message: " << message << std::endl;
}

void validateDNA(std::string& s){
    for(size_t i = 0; i < s.length(); i++){
        if(s[i] != 'A' && s[i] != 'C' && s[i] != 'G' && s[i] != 'T'){
            s.clear();
            return;
        }
    }
    if(s.length() % 3 != 0){
        s = s.substr(0, s.length() - (s.length() % 3));
    }
}

void validateMSG(std::string& s){
    for(size_t i = 0; i < s.length(); i++){
        if(!isalpha(s[i]) && s[i] != ' ' && s[i] != '.' && s[i] != ',' && s[i] != '!' && s[i] != '?'){
            s.clear();
        }
    }
}

void encode(std::string& s){
    std::string code = "";
    for(size_t i = 0; i < s.length(); i++){
        unsigned val = 0;
        if(isupper(s[i])){
            val = s[i] - 'A' + 37;
        }
        else if(islower(s[i])){
            val = s[i] - 'a';
        }
        else{
            switch(s[i]){
                case ' ':
                    val = 26;
                    break;
                case '.':
                    val = 27;
                    break;
                case ',':
                    val = 28;
                    break;
                case '!':
                    val = 29;
                    break;
                case '?':
                    val = 30;
                    break;
            }
        }
        std::string codon = std::string(3, ' ');
        for(size_t j = 0; j < 3; j++){
            switch(val % 4){
                case 0:
                    codon[2-j] = 'A';
                    break;
                case 1:
                    codon[2-j] = 'C';
                    break;
                case 2:
                    codon[2-j] = 'G';
                    break;
                case 3:
                    codon[2-j] = 'T';
                    break;
            }
            val /= 4;
        }
        code += codon;
    }
    std::cout << "DNA code: " << code << std::endl;
}