CSC1321 Programming Assignment: Arrays and Functions

1. Write a Cipher

   Write a cipher that encodes a plain text message and decodes back to the original message. The cipher takes an input text message and a key (a sequence of numbers) and then arranges the characters of the message into a 2D grid. And then read off the characters from the grid column by column as an encoded message in the order specified by the column numbers in the key. Decoding is just a reverse process of the encoding above.
   Hint: To convert a digit character to its corresponding number, just use the coding value difference. For example: '5' - '0' gives a number of 5.

   //Sample main() function
   
   #include <iostream>
   #include <string>
   
   using namespace std;
   
   void print(char b[], int size);
   void encode(char m[], int msgSize, char key[], int gridWidth);
   void decode(char m[], int msgSize, char key[], int gridWidth);
   
   int main()
   {
       string msg;   //Original plain text message
       string key;   //A sequence of numbers used for the order of the columns of a grid to be read off. 
       int size;     //The number of characters in the original message
       int length;   //The length of the key for encoding 
   
       cout << "Enter a plain text message for encoding" << endl;
       getline(cin, msg);
   
       cout << "Enter a key for encoding: " << endl;
       cin >> key;
   
       cout << endl;
   
       size = msg.length();
       length = key.length();
   
       //If the length of the string message is not a multiple of the length of the key,
       //cut off some trailing characters of the message to make it so.
   
       msg = msg.substr(0, size / length * length);
       size = msg.length();
   
       //char msg_arr[size + 1];   //Create an array of characters for storing the original message 
       //char key_arr[length + 1];   //Create an array of digits for the key 
   
       char * msg_arr = new char[size + 1];   //Create an array of characters for storing the original message 
       char * key_arr = new char[length + 1];   //Create an array of digits for the key 
   
       strcpy_s(msg_arr, size+1, msg.c_str());  //Copy the original string message to the character array with no more than size + 1 elements
       strcpy_s(key_arr, length+1, key.c_str());  //Copy the key to the character array with no more than length + 1 elements
   
       cout << "Original plain text message: " << endl;
       print(msg_arr, size);
       print(key_arr, length);
   
       cout << endl;
       encode(msg_arr, size, key_arr, length);
       cout << "Encoded message: " << endl;
       print(msg_arr, size);
   
       cout << endl;
       decode(msg_arr, size, key_arr, length);
       cout << "Decoded message: " << endl;
       print(msg_arr, size);
   
       return 0;
   }
   
   //Sample output:
   
   Enter a plain text message for encoding
   YOURCELLPHONEHASBEENSTOLENDELETEDATAATONCE
   Enter a key for encoding: 
   31452
   
   Message looks like in a 2D grid:
   YOURC
   ELLPH
   ONEHA
   SBEEN
   STOLE
   NDELE
   TEDAT
   AATON
   
   Message looks like after transposition:
   ULEEOEDT
   YEOSSNTA
   RPHELLAO
   CHANEETN
   OLNBTDEA
   
   Encoded message: 
   ULEEOEDTYEOSSNTARPHELLAOCHANEETNOLNBTDEA
   
   Decoded message: 
   YOURCELLPHONEHASBEENSTOLENDELETEDATAATON
   
   

2. Connect Four (Bonus)

   Connect four is a two-player board game in which the players alternately drop colored disks into a seven-column, six-row vertically suspended grid, as shown in this real game picture. The objective of the game is to connect four same-colored disks in a row, a col- umn, or a diagonal before your opponent can do likewise. The program prompts two players to drop a RED or YELLOW disk alternately. Whenever a disk is dropped, the program redisplays the board on the console and determines the status of the game (win, draw, or continue). Here is a sample run:

   

//Skeleton program for main function
int main() 
{
    char board[6][7];

    displayBoard(board);

    while (true) {
      // Prompt the first player
      dropADisc('R', board);
      
      displayBoard(board);
      if (isWon(board)) 
	  {
        cout << "The red player won" << endl;
        break;
      }
      else if (isDraw(board)) 
	  {
        cout << "No winner" << endl;
        break;
      }

      // Prompt the second player
      dropADisc('Y', board);
      displayBoard(board);

      if (isWon(board)) 
	  {
        cout << "The yellow player won" << endl;
        break;
      }
      else if (isDraw(board)) 
	  {
        cout << "No winner" << endl;
        break;
      }
    }
}