p4_23.cpp

logo语言中的“龟图”

// Exercise 4.23 Solution
#include <iostream.h>

const int MAXCOMMANDS = 100, SIZE = 20;

int turnRight( int );
int turnLeft( int );
void getCommands( int [][ 2 ] );
void movePen( int, int [][ SIZE ], int, int );
void printArray( const int [][ SIZE ] );

int main()
{
   int floor[ SIZE ][ SIZE ] = { 0 }, command, direction = 0,
       commandArray[ MAXCOMMANDS ][ 2 ] = { 0 }, distance, count = 0;
   bool penDown = false;

   getCommands( commandArray );
   command = commandArray[ count ][ 0 ];
   
   while ( command != 9 ) {
      switch ( command ) {
         case 1:
            penDown = false;
            break;
         case 2:
            penDown = true;
            break;
         case 3:
            direction = turnRight( direction );
            break;
         case 4:
            direction = turnLeft( direction );
            break;
         case 5:
            distance = commandArray[ count ][ 1 ];
            movePen( penDown, floor, direction, distance );
            break;
         case 6:
            cout << "\nThe drawing is:\n\n";
            printArray( floor );
            break;
      }
      
      command = commandArray[ ++count ][ 0 ]; 
   }

   return 0;
}

void getCommands( int commands[][ 2 ] )
{
   int tempCommand;

   cout << "Enter command (9 to end input): ";
   cin >> tempCommand;
   
   for ( int i = 0; tempCommand != 9 && i < MAXCOMMANDS; ++i ) {
      commands[ i ][ 0 ] = tempCommand;

      if ( tempCommand == 5 ) {
         cin.ignore();   // skip comma
         cin >> commands[ i ][ 1 ];
      }

      cout << "Enter command (9 to end input): ";
      cin >> tempCommand;
   }

   commands[ i ][ 0 ] = 9;  // last command
}

int turnRight( int d ) 
{
   return ++d > 3 ? 0 : d;
}

int turnLeft( int d ) 
{
   return --d < 0 ? 3 : d;
}

void movePen( int down, int a[][ SIZE ], int dir, int dist )
{
   static int xPos = 0, yPos = 0;
   int j;  // looping variable

   switch ( dir ) {
      case 0:   // move to the right
         for ( j = 1; j <= dist && yPos + j < SIZE; ++j )
            if ( down )
               a[ xPos ][ yPos + j ] = 1;

         yPos += j - 1;
         break;
      case 1:   // move down
         for ( j = 1; j <= dist && xPos + j < SIZE; ++j )
            if ( down )
               a[ xPos + j ][ yPos ] = 1;
            
         xPos += j - 1;
         break;
      case 2:   // move to the left
         for ( j = 1; j <= dist && yPos - j >= 0; ++j )
            if ( down )
               a[ xPos ][ yPos - j ] = 1;
            
         yPos -= j - 1;
         break;
      case 3:   // move up
         for ( j = 1; j <= dist && xPos - j >= 0; ++j )
            if ( down )
               a[ xPos - j ][ yPos ] = 1;
            
         xPos -= j - 1;
         break;
   }
}

void printArray( const int a[][ SIZE ] )
{
   for ( int i = 0; i < SIZE; ++i ) {
      for ( int j = 0; j < SIZE; ++j )
         cout << ( a[ i ][ j ] ? '*' : ' ' );
      
      cout << endl;
   }
}