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How do I remove the  jumps in this code

Posted on 2008-10-03
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Last Modified: 2010-04-15
How would be the best way to eliminate the break and continue jumps in this code as well as the infinite for(; ;) loop...

This comes from Ivor Hortons C book-reversi program- his code is not usually student friendly...


/* Program 9.9 REVERSI An Othello type game */

#include <stdio.h>

#include <ctype.h>
 

#define SIZE 6  /* Board size - must be even */
 

/* Function prototypes */

void display(char board[][SIZE]);

int valid_moves(char board[][SIZE], int moves[][SIZE], char player); 

void make_move(char board[][SIZE], int row, int col, char player);  

void computer_move(char board[][SIZE], int moves[][SIZE], char player);  

int best_move(char board[][SIZE], int moves[][SIZE], char player);

int get_score(char board[][SIZE], char player);
 

int main()

{

  char board [SIZE][SIZE] = { 0 };  /* The board           */

  int moves[SIZE][SIZE] = { 0 };    /* Valid moves         */

  int row = 0;                      /* Board row index     */

  int col = 0;                      /* Board column index  */

  int no_of_games = 0;              /* Number of games     */

  int no_of_moves = 0;              /* Count of moves      */

  int invalid_moves = 0;            /* Invalid move count  */

  int comp_score = 0;               /* Computer score      */

  int user_score = 0;               /* Player score        */

  char y = 0;                       /* Column letter       */

  int x = 0;                        /* Row number          */

  char again = 0;                   /* Replay choice input */

  int player = 0;                   /* Player indicator    */
 

   printf("\nREVERSI\n\n");

  printf("You can go first on the first game, then we will take turns.\n");

  printf("   You will be white - (O)\n   I will be black   - (@).\n");

  printf("Select a square for your move by typing a digit for the row\n "

	  "and a letter for the column with no spaces between.\n");

  printf("\nGood luck!  Press Enter to start.\n");

  scanf("%c", &again);
 

   /* Prompt for how to play - as before */
 

   /* The main game loop */

   do

   {

     /* On even games the player starts; */

     /* on odd games the computer starts */

     player = ++no_of_games % 2; 

     no_of_moves = 4;                /* Starts with four counters */
 

     /* Blank all the board squares */    

     for(row = 0; row < SIZE; row++)

       for(col = 0; col < SIZE; col++)

         board[row][col] = ' ';
 

     /* Place the initial four counters in the center */

     board[SIZE/2 - 1][SIZE/2 - 1] = board[SIZE/2][SIZE/2] = 'O';

     board[SIZE/2 - 1][SIZE/2] = board[SIZE/2][SIZE/2 - 1] = '@';
 

     /* The game play loop */

     do

     {

       display(board);             /* Display the board  */

       if(player++ % 2)

       { /*   It is the player's turn                    */

         if(valid_moves(board, moves, 'O'))

         {

           /* Read player moves until a valid move is entered */

           for(;;)

           {

             fflush(stdin);              /* Flush the keyboard buffer */

             printf("Please enter your move (row column): "); 

             scanf("%d%c", &x, &y);              /* Read input        */

             y = tolower(y) - 'a';         /* Convert to column index */

             x--;                          /* Convert to row index    */

             if( x>=0 && y>=0 && x<SIZE && y<SIZE && moves[x][y])

             {

               make_move(board, x, y, 'O');

               no_of_moves++;              /* Increment move count */

               break;

             }

             else

               printf("Not a valid move, try again.\n");

           }

         }

         else                              /* No valid moves */

           if(++invalid_moves<2)

           {

             fflush(stdin);

             printf("\nYou have to pass, press return");

             scanf("%c", &again);

           }

           else

             printf("\nNeither of us can go, so the game is over.\n");

       }

       else

       { /* It is the computer's turn                    */

         if(valid_moves(board, moves, '@')) /* Check for valid moves */

         {

           invalid_moves = 0;               /* Reset invalid count   */

           computer_move(board, moves, '@');

           no_of_moves++;                   /* Increment move count  */

         }

         else

         {

           if(++invalid_moves<2)

             printf("\nI have to pass, your go\n"); /* No valid move */

           else

             printf("\nNeither of us can go, so the game is over.\n");

         }

       }

     }while(no_of_moves < SIZE*SIZE && invalid_moves<2);
 

     /* Game is over */

     display(board);  /* Show final board */
 

     /* Get final scores and display them */

     comp_score = user_score = 0; 

     for(row = 0; row < SIZE; row++)

       for(col = 0; col < SIZE; col++)

       {

         comp_score += board[row][col] == '@';

         user_score += board[row][col] == 'O';

       }

     printf("The final score is:\n");

     printf("Computer %d\n    User %d\n\n", comp_score, user_score);
 

     fflush(stdin);               /* Flush the input buffer */

     printf("Do you want to play again (y/n): ");

     scanf("%c", &again);         /* Get y or n             */

   }while(tolower(again) == 'y'); /* Go again on y          */
 

   printf("\nGoodbye\n"); 

   

   return 0;

}
 

/***********************************************

 * Function to display the board in it's       *

 * current state with row numbers and column   *

 * letters to identify squares.                *

 * Parameter is the board array.               *

 ***********************************************/

void display(char board[][SIZE])

{

   int row  = 0;          /* Row index      */

   int col = 0;           /* Column index   */

   char col_label = 'a';  /* Column label   */
 

   printf("\n ");         /* Start top line */

   for(col = 0 ; col<SIZE ;col++)

     printf("   %c", col_label+col); /* Display the top line */

   printf("\n");                     /* End the top line     */
 

   /* Display the intermediate rows */  

   for(row = 0; row < SIZE; row++)

   {

     printf("  +");

     for(col = 0; col<SIZE; col++)

       printf("---+");

     printf("\n%2d|",row + 1); 
 

     for(col = 0; col<SIZE; col++)

       printf(" %c |", board[row][col]);  /* Display counters in row */

     printf("\n");    

   }
 

   printf("  +");                  /* Start the bottom line   */

   for(col = 0 ; col<SIZE ;col++)

     printf("---+");               /* Display the bottom line */

   printf("\n");                   /* End the bottom  line    */

}
 

/***********************************************

/* Calculates which squares are valid moves    *

 * for player. Valid moves are recorded in the *

 * moves array - 1 indicates a valid move,     *

 * 0 indicates an invalid move.                *

 * First parameter is the board array          *

 * Second parameter is the moves array         *

 * Third parameter identifies the player       *

 * to make the move.                           *

 * Returns valid move count.                   *

 ***********************************************/

int valid_moves(char board[][SIZE], int moves[][SIZE], char player)

{

   int rowdelta = 0;     /* Row increment around a square    */

   int coldelta = 0;     /* Column increment around a square */

   int row = 0;          /* Row index                        */

   int col = 0;          /* Column index                     */

   int x = 0;            /* Row index when searching         */

   int y = 0;            /* Column index when searching      */

   int no_of_moves = 0;  /* Number of valid moves            */
 

   /* Set the opponent            */

   char opponent = (player == 'O')? '@' : 'O';    
 

   /* Initialize moves array to zero */

   for(row = 0; row < SIZE; row++)

     for(col = 0; col < SIZE; col++)

       moves[row][col] = 0;
 

   /* Find squares for valid moves.                           */

   /* A valid move must be on a blank square and must enclose */

   /* at least one opponent square between two player squares */

   for(row = 0; row < SIZE; row++)

     for(col = 0; col < SIZE; col++)

     {

       if(board[row][col] != ' ')   /* Is it a blank square?  */

         continue;                  /* No - so on to the next */
 

       /* Check all the squares around the blank square  */ 

       /* for the opponents counter                      */

       for(rowdelta = -1; rowdelta <= 1; rowdelta++)

         for(coldelta = -1; coldelta <= 1; coldelta++)

         { 

           /* Don't check outside the array, or the current square */

           if(row + rowdelta < 0 || row + rowdelta >= SIZE ||

              col + coldelta < 0 || col + coldelta >= SIZE || 

                                       (rowdelta==0 && coldelta==0))

             continue;
 

           /* Now check the square */

           if(board[row + rowdelta][col + coldelta] == opponent)

           {

             /* If we find the opponent, move in the delta direction  */

             /* over opponent counters searching for a player counter */

             x = row + rowdelta;                /* Move to          */

             y = col + coldelta;                /* opponent square  */
 

             /* Look for a player square in the delta direction */

             for(;;)

             {

               x += rowdelta;                  /* Go to next square */

               y += coldelta;                  /* in delta direction*/
 

               /* If we move outside the array, give up */

               if(x < 0 || x >= SIZE || y < 0 || y >= SIZE)

                 break;
 

               /* If we find a blank square, give up */ 

               if(board[x][y] == ' ')

                 break;

                /*  If the square has a player counter */

                /*  then we have a valid move          */

               if(board[x][y] == player)

               {

                 moves[row][col] = 1;   /* Mark as valid */

                 no_of_moves++;         /* Increase valid moves count */

                 break;                 /* Go check another square    */

               }

             } 

           } 

         }  

     }

   return no_of_moves; 

}
 

/*******************************************************************

 * Finds the best move for the computer. This is the move for      *

 * which the opponent's best possible move score is a minimum.     *

 * First parameter is the board array.                             *

 * Second parameter is the moves array containing valid moves.     *

 * Third parameter identifies the computer.                        *

 *******************************************************************/

void computer_move(char board[][SIZE], int moves[][SIZE], char player)

{

   int row = 0;                          /* Row index               */

   int col = 0;                          /* Column index            */

   int best_row = 0;                     /* Best row index          */

   int best_col = 0;                     /* Best column index       */

   int i = 0;                            /* Loop index              */

   int j = 0;                            /* Loop index              */

   int new_score = 0;                    /* Score for current move  */

   int score = 100;                      /* Minimum opponent score  */

   char temp_board[SIZE][SIZE];          /* Local copy of board     */

   int temp_moves[SIZE][SIZE];           /* Local valid moves array */

   char opponent = (player == 'O')? '@' : 'O'; /* Identify opponent */
 

   /* Go through all valid moves */

   for(row = 0; row < SIZE; row++)

     for(col = 0; col < SIZE; col++)

     {

       if(moves[row][col] == 0)

         continue;

 

       /* First make copies of the board and moves arrays */

       for(i = 0; i < SIZE; i++)

         for(j = 0; j < SIZE; j++)

           temp_board[i][j] = board[i][j];

   

       /* Now make this move on the temporary board */

       make_move(temp_board, row, col, player); 
 

       /* find valid moves for the opponent after this move */

       valid_moves(temp_board, temp_moves, opponent);
 

       /* Now find the score for the opponents best move */

       new_score = best_move(temp_board, temp_moves, opponent);
 

       if(new_score<score)    /* Is it worse?           */

       {                      /* Yes, so save this move */

         score = new_score;   /* Record new lowest opponent score */

         best_row = row;  /* Record best move row             */

         best_col = col;  /* and column                       */

       }

     }
 

   /* Make the best move */

   make_move(board, best_row, best_col, player); 

}
 

/*******************************************************************

 * Calculates the score for the current board position for the     *

 * player. player counters score +1, opponent counters score -1    *

 * First parameter is the board array                              *

 * Second parameter identifies the player                          *

 * Return value is the score.                                      *

 *******************************************************************/

int get_score(char board[][SIZE], char player)

{

   int score = 0;      /* Score for current position */

   int row = 0;        /* Row index                  */    

   int col = 0;        /* Column index               */

   char opponent = player == 'O' ? '@' : 'O';  /* Identify opponent */
 

   /* Check all board squares */

   for(row = 0; row < SIZE; row++)

     for(col = 0; col < SIZE; col++)

   { 

     score -= board[row][col] == opponent; /* Decrement for opponent */

     score += board[row][col] == player;   /* Increment for player   */

   }

   return score;	   

}
 

/*******************************************************************

 * Calculates the score for the best move out of the valid moves   *

 * for player in the current position.                             *

 * First parameter is the board array                              *

 * Second parameter is the moves array defining valid moves.       *

 * Third parameter identifies the player                           *

 * The score for the best move is returned                         *

 *******************************************************************/

int best_move(char board[][SIZE], int moves[][SIZE], char player)

{

   int row = 0;     /* Row index    */

   int col = 0;     /* Column index */

   int i = 0;       /* Loop index   */

   int j = 0;       /* Loop index   */
 

   char opponent = player=='O'?'@':'O'; /* Identify opponent */
 

   char new_board[SIZE][SIZE] = { 0 };  /* Local copy of board    */

   int score = 0;                       /* Best score             */

   int new_score = 0;                   /* Score for current move */
 

   /* Check all valid moves to find the best */

   for(row = 0 ; row<SIZE ; row++)

     for(col = 0 ; col<SIZE ; col++)

     {

       if(!moves[row][col])             /* Not a valid move?      */

         continue;                      /* Go to the next         */

 

       /* Copy the board */

       for(i = 0 ; i<SIZE ; i++)

         for(j = 0 ; j<SIZE ; j++)

           new_board[i][j] = board[i][j];
 

       /* Make move on the board copy */

       make_move(new_board, row, col, player);  
 

       /* Get score for move */

       new_score = get_score(new_board, player);  
 

       if(score<new_score)         /* Is it better?               */

               score = new_score;  /* Yes, save it as best score  */

     }

   return score;                   /* Return best score           */

}
 

/********************************************************************

 * Makes a move. This places the counter on a square,and reverses   *

 * all the opponent's counters affected by the move.                *

 * First parameter is the board array.                              *

 * Second and third parameters are the row and column indices.      *

 * Fourth parameter identifies the player.                          *

 ********************************************************************/

void make_move(char board[][SIZE], int row, int col, char player)

{

   int rowdelta = 0;                   /* Row increment              */

   int coldelta = 0;                   /* Column increment           */

   int x = 0;                          /* Row index for searching    */

   int y = 0;                          /* Column index for searching */

   char opponent = (player == 'O')? '@' : 'O';  /* Identify opponent */
 

   board[row][col] = player;           /* Place the player counter   */
 

   /* Check all the squares around this square */

   /* for the opponents counter                */

   for(rowdelta = -1; rowdelta <= 1; rowdelta++)

     for(coldelta = -1; coldelta <= 1; coldelta++)

     { 

       /* Don't check off the board, or the current square */

       if(row + rowdelta < 0 || row + rowdelta >= SIZE ||

          col + coldelta < 0 || col + coldelta >= SIZE || 

                               (rowdelta==0 && coldelta== 0))

         continue;
 

       /* Now check the square */

       if(board[row + rowdelta][col + coldelta] == opponent)

       {

         /* If we find the opponent, search in the same direction */

         /* for a player counter                                  */

         x = row + rowdelta;        /* Move to opponent */

         y = col + coldelta;        /* square           */
 

         for(;;)

         {

           x += rowdelta;           /* Move to the      */

           y += coldelta;           /* next square      */ 
 

           /* If we are off the board give up */

           if(x < 0 || x >= SIZE || y < 0 || y >= SIZE)

             break;

 

           /* If the square is blank give up */

           if(board[x][y] == ' ')

             break;
 

           /* If we find the player counter, go backwards from here */

           /* changing all the opponents counters to player         */

           if(board[x][y] == player)

           {

             while(board[x-=rowdelta][y-=coldelta]==opponent) /* Opponent? */

               board[x][y] = player;    /* Yes, change it */

             break;                     /* We are done    */

           } 

         }

       }

     }

}

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Question by:CPlusJavaCSharp
3 Comments
 
LVL 45

Accepted Solution

by:
sunnycoder earned 300 total points
ID: 22639493
>How would be the best way to eliminate the break and continue jumps in this code as well as the infinite for(; ;) loop..
move the break statement to loop exit condition ... e.g.
          flag = 1;
          for(;flag;)
           {
             fflush(stdin);              /* Flush the keyboard buffer */
             printf("Please enter your move (row column): ");
             scanf("%d%c", &x, &y);              /* Read input        */
             y = tolower(y) - 'a';         /* Convert to column index */
             x--;                          /* Convert to row index    */
             flag = x>=0 && y>=0 && x<SIZE && y<SIZE && moves[x][y];
             if( flag)
             {
               make_move(board, x, y, 'O');
               no_of_moves++;              /* Increment move count */
               break;
             }
             else
               printf("Not a valid move, try again.\n");
           }

To remove a continue, just put everything that follows in an else


       for(rowdelta = -1; rowdelta <= 1; rowdelta++)
         for(coldelta = -1; coldelta <= 1; coldelta++)
         {
           /* Don't check outside the array, or the current square */
           if(row + rowdelta < 0 || row + rowdelta >= SIZE ||
              col + coldelta < 0 || col + coldelta >= SIZE ||
                                       (rowdelta==0 && coldelta==0))
             //continue;
            {
            }
            else {
 
           /* Now check the square */
           if(board[row + rowdelta][col + coldelta] == opponent)
           {
             /* If we find the opponent, move in the delta direction  */
             /* over opponent counter
               ...
           }
         } //end else

Bottom line is moving the skip/jump to start/end of loop.

Break and continue are very commonly used statements. It is mostly goto's that are hard to follow. I would suggest taking things a little slow and working out the breaks and continues.
0
 
LVL 23

Expert Comment

by:Mysidia
ID: 22639594
You can replace for(;;)  as follows
while(1) { ...code...   }

Keep the break statements, they aren't bad in that situation.
This is terser, clearer, and generally more preferable.


Or

loop_block:
   {  
       ...code...
          goto exit_loop;    // in place of break
   }
goto loop_block;
exit_loop:


I just want to emphasize  that you should not seek to eliminate common statements
for the sake of eliminating common statements.

Stick with what is simple, and gets the job done in the straightforward way, with minimal  syntactic clutter.

0
 
LVL 6

Expert Comment

by:RishadanPort
ID: 22640375
I personally like infinite for loops
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