Thread: Would you help me understand this code?

Please explain me each sentence in this code, Thanks.

Code:

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

void swap(int *a, int *b)
{
    int c = *a;
    *a = *b;
    *b = c;
}

void draw(int board[3][3])
{
    int i, j;
    printf("\n");
    for(i = 0; i < 3; i++)
        for(j = 0; j < 3; j++)
        {
            if(board[i][j] != 0)
                printf(" |%d|", board[i][j]);
            else
                printf(" | |");
            if(j == 2)
                printf("\n ----------- \n");
        }            
}

int main()
{
    int board[3][3], *p = (int*)board;
    int i, j, c, x, ei, ej;
    
    //initialization
    for(i = 0, c = 8; i < 3; i++)
        for(j = 0; j < 3; j++, c--)
            board[i][j] = c;
    board[ei = 2][ej = 2] = 0;
     
     // check move //
    c = 0;
    while(c < 8)
    {
        draw(board);
        printf(" Move ");
        x = getchar() - 49 + 1;
        if((x < 10) && (x > 0))
            printf("%d\n",x);
        else 
        {
            printf("bad move\n");
            continue;
        }
        
        if(ei > 0 && board[ei - 1][ej] == x)
        {
            swap(&board[ei][ej], &board[ei - 1][ej]);
            ei--;
        }
        else if(ei < 2 && board[ei + 1][ej] == x)
        {
            swap(&board[ei][ej], &board[ei + 1][ej]);
            ei++;
        }
        else if(ej > 0 && board[ei][ej - 1] == x)
        {
            swap(&board[ei][ej], &board[ei][ej - 1]);
            ej--;
        }
        else if(ej < 2 && board[ei][ej + 1] == x)
        {
            swap(&board[ei][ej], &board[ei][ej + 1]);
            ej++;
        }
        else 
        {
            printf("bad move\n");
            continue;
        }
        
        // check win //
        for(c = 0; c < 8; c++)
            if(p[c] != c + 1)
                break;             
    }
    
    draw(board);
    printf("\n You Win!");
    getchar();
    return 0;
}

Anyone?

Dude do you seriously expect anyone to explain a hundred lines of code to you one by one? Maybe start by asking what part don't understand, then someone should explain.

Alright then,
just explain me this part

Code:

int main()
{
    int board[3][3], *p = (int*)board;
    int i, j, c, x, ei, ej;
    
    //initialization
    for(i = 0, c = 8; i < 3; i++)
        for(j = 0; j < 3; j++, c--)
            board[i][j] = c;
    board[ei = 2][ej = 2] = 0;
     
     // check move //
    c = 0;
    while(c < 8)
    {
        draw(board);
        printf(" Move ");
        x = getchar() - 49 + 1;
        if((x < 10) && (x > 0))
            printf("&#37;d\n",x);
        else 
        {
            printf("bad move\n");
            continue;
        }
        
        if(ei > 0 && board[ei - 1][ej] == x)
        {
            swap(&board[ei][ej], &board[ei - 1][ej]);
            ei--;
        }
        else if(ei < 2 && board[ei + 1][ej] == x)
        {
            swap(&board[ei][ej], &board[ei + 1][ej]);
            ei++;
        }
        else if(ej > 0 && board[ei][ej - 1] == x)
        {
            swap(&board[ei][ej], &board[ei][ej - 1]);
            ej--;
        }
        else if(ej < 2 && board[ei][ej + 1] == x)
        {
            swap(&board[ei][ej], &board[ei][ej + 1]);
            ej++;
        }
        else 
        {
            printf("bad move\n");
            continue;
        }
        
        // check win //
        for(c = 0; c < 8; c++)
            if(p[c] != c + 1)
                break;             
    }
    
    draw(board);
    printf("\n You Win!");
    getchar();
    return 0;
}

Homework? If so, pay attention in class. I just started learning and know some of what is going on. Just Study up seeing as I don't think anyone is going to tell you line by line.

well, i dont think anyone is going to try to explain this to you just out of principle.
this kind of falls into that no homework questions/do this for me area.
not to be rude or anything, im just trying to give advice.
honestly, if you want to find out what it means, i would start with the basics.
theres a tutorial here if you want to learn it though.

oh, and just for future reference, dont do this:

Code:

//initialization
    for(i = 0, c = 8; i < 3; i++)
        for(j = 0; j < 3; j++, c--)
            board[i][j] = c;
                board[ei = 2][ej = 2] = 0;

from what i understand, this is a bad way to initialize variables.
and just looking at it, the code itself wouldnt work.
'why?' you might ask?
read the tutorial

It works perfectly mate, I just checked it.

I use Geany.

I don't want people to explain me what it does, I want people to explain me the lines of this program, I can't understand it.

when you detect inflicted confusion say stop.

if else.
arrays.
&&.
multidimensional arrays.
for loops.
arithmetic.

No..
My question is why did the author typed: board[ei - 1][ej] and not board[ei - 5265][ej].
How can I explain.

I don't understand why he typed this: if(ei > 0 && board[ei - 1][ej] == x) for example, and the other things.

ei > 0 is a range check. I think the other part is something to do with the game rules. what is the program for?

Run it, it's hard to explain.

Originally Posted by eXeCuTeR

Run it, it's hard to explain.

oh ok now I get it...

ei, ej is where the current position is. and -1 is the offset that you are trying to move. the if else tree is for one of four possible moves.