Game of fifteen move function duplicating "_"

Question

My move function is duplicating the blank tiles instead of swapping. I even checked for the boundary conditions. It swaps immediate left and right ones, but the ones on top and beyond (illegal move) are duplicated. Here is my entire code:

#define _XOPEN_SOURCE 500

#include <cs50.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

// constants
#define DIM_MIN 3
#define DIM_MAX 9

// board
int board[DIM_MAX][DIM_MAX];

// dimensions
int d;

// prototypes
void clear(void);
void greet(void);
void init(void);
void draw(void);
bool move(int tile);
bool won(void);
void swap(int *i, int *j);

int main(int argc, string argv[])
{
    // ensure proper usage
    if (argc != 2)
    {
        printf("Usage: fifteen d\n");
        return 1;
    }

    // ensure valid dimensions
    d = atoi(argv[1]);
    if (d < DIM_MIN || d > DIM_MAX)
    {
        printf("Board must be between %i x %i and %i x %i, inclusive.\n",
            DIM_MIN, DIM_MIN, DIM_MAX, DIM_MAX);
        return 2;
    }

    // open log
    FILE *file = fopen("log.txt", "w");
    if (file == NULL)
    {
        return 3;
    }

    // greet user with instructions
    greet();

    // initialize the board
    init();

    // accept moves until game is won
    while (true)
    {
        // clear the screen
        clear();

        // draw the current state of the board
        draw();

        // log the current state of the board (for testing)
        for (int i = 0; i < d; i++)
        {
            for (int j = 0; j < d; j++)
            {
                fprintf(file, "%i", board[i][j]);
                if (j < d - 1)
                {
                    fprintf(file, "|");
                }
            }
            fprintf(file, "\n");
        }
        fflush(file);

        // check for win
        if (won())
        {
            printf("ftw!\n");
            break;
        }

        // prompt for move
        printf("Tile to move: ");
        int tile = get_int();

        // quit if user inputs 0 (for testing)
        if (tile == 0)
        {
            break;
        }

        // log move (for testing)
        fprintf(file, "%i\n", tile);
        fflush(file);

        // move if possible, else report illegality
        if (!move(tile))
        {
            printf("\nIllegal move.\n");
            usleep(500000);
        }

        // sleep thread for animation's sake
        usleep(500000);
    }

    // close log
    fclose(file);

    // success
    return 0;
}

/**
 * Clears screen using ANSI escape sequences.
 */
void clear(void)
{
    printf("\033[2J");
    printf("\033[%d;%dH", 0, 0);
}

/**
 * Greets player.
 */
void greet(void)
{
    clear();
    printf("WELCOME TO GAME OF FIFTEEN\n");
    usleep(2000000);
}

/**
 * Initializes the game's board with tiles numbered 1 through d*d - 1
 * (i.e., fills 2D array with values but does not actually print them).  
 */
void init(void)
{ 
    int n = 1;
    for (int i=0; i<d; i++)
    {
        for (int j=0; j<d; j++)
        {
            board [i][j] = (d*d) - n;
            n=n+1;

        }
    }
    board [d-1][d-1] = 0;

    if (d%2 == 0)
    {
        swap(&(board[d-1][d-3]), &(board[d-1][d-2]));
    }
}

/**
 * Prints the board in its current state.
 */
void draw(void)
{
    for (int i=0; i<d; i++)
    {
        for (int j=0; j<d; j++)
        {
            if (board[i][j]!= 0)
            {
                printf("%2i", board[i][j]);
            }
            else if (board[i][j] == 0)
            {
                printf("%2c", 95);
            }

        }
        printf("\n");
    }
}

/**
 * If tile borders empty space, moves tile and returns true, else
 * returns false. 
 */
bool move(int tile)
{

    for (int i=0; i<d; i++)
    {
        for (int j=0; j<d; j++)
        {
            if (board[i][j] == tile)
            {
                if(i>0 && board[i][j-1] == 0)
                {
                    board[i][j-1] = tile;
                    board[i][j] = 0;
                    return true;
                }

                if(i>0 && board[i][j+1] == 0)
                {
                    board[i][j+1] = tile;
                    board[i][j] = 0;
                    return true;
                }

                if(j<d-1 && board[i-1][j]==0)
                {
                    board[i-1][j] = tile;
                    board[i][j] = 0;
                    return true;
                }


                if(j<d-1 && board[i+1][j] == 0)
                {
                    board[i+1][j] = tile;
                    board[i][j] = 0;
                    return true;
                }

         }

        }

    }
    return false;
}

/**
 * Returns true if game is won (i.e., board is in winning configuration), 
 * else false.
 */
bool won(void)
{
    // TODO
    return false;
}

void swap(int *i, int *j)
{
    int temp = *i;
    *i = *j;
    *j = temp;

}

Answer 1

The code is going off the edge of the board. Look at the following:

        if(i>0 && board[i][j-1] == 0)

You had the right idea, but mixed your i's and j's. The var that 1 is being added or subtracted to is the var that needs to be validated.

And like DinoCoderSaurus says, please learn to format your code in questions correctly. Because of this, I didn't do a deep dive analysis, so there may be other issues.

If this answers your question, please click on the check mark to accept. Let's keep up on forum maintenance. ;-)