do-while loop wont exit in C

Question

Ok, I'm sorry in advance, I know there is a thousand examples of how do-while loops work and how to exit them. I swear I've tried them all. For the life of me, I cannot get this to exit when the user enters a 0. There has to be something I'm over-looking. How I got the one to work inside the else if loop but the main one is beyond me. I would appreciate any help or direction.

int main()
{
    char connectBoard[6][7];
    int i , j;
    char c;
    int turn = 1;
    char player1 = 'x';
    char player2 = 'o';
    int spot;

    for( i = 0; i < 6; i++) //sets up 2D array board
    {
        for( j = 0; j < 7; j++)
        {
            c = '.';
            connectBoard[i][j] = c;
        }
    }
    for( i = 0; i < 6; i++)// prints out 2D array board
    {
        for( j = 0; j < 7; j++)
        {
            printf("%c", connectBoard[i][j]);
        }
        printf("\n");
    }
    printf("=======\n");
    printf("1234567\n");

    do{
        if( turn%2 != 0 ) //player1 turn
        {
            for( i = 5; i < 6; i++)
            {
                for(j = 0; j < 1; j++)
                {
                    printf(" Player %c, drop your piece in which column (1-7 or 0 to quit): ", player1);
                    scanf("%d", &spot);
                    j = spot - 1;
                    if( connectBoard[i][j] == '.' )
                    {
                        connectBoard[i][j] = 'x';
                    }
                    else if( connectBoard[i][j] == 'x' || connectBoard[i][j] == 'o' )
                    {
                        do
                        {
                            i--;
                        }while(connectBoard[i][j] == 'x' || connectBoard[i][j] == 'o');
                        connectBoard[i][j] = 'x';
                        if( i == -1 )
                        {
                            printf("***Bad entry, try again: ");
                            scanf("%d", &spot);
                            j = spot - 1;
                            i = 5;
                            connectBoard[i][j] = 'x';
                        }
                    }
                    turn++;
                }
                break;
            }
            printf("\n");
            for( i = 0; i < 6; i++)// prints out 2D array board
            {
                for( j = 0; j < 7; j++)
                {
                    printf("%c", connectBoard[i][j]);
                }
                printf("\n");
            }
            printf("=======\n");
            printf("1234567\n");
        }
        if( turn%2 == 0 ) //player2 turn
        {
            for( i = 5; i < 6; i++)
            {
                for(j = 0; j < 1; j++)
                {
                    printf(" Player %c, drop your piece in which column (1-7 or 0 to quit): ", player2);
                    scanf("%d", &spot);
                    j = spot - 1;
                    if( connectBoard[i][j] == '.' )
                    {
                        connectBoard[i][j] = 'o';
                    }
                    else if( connectBoard[i][j] == 'x' || connectBoard[i][j] == 'o' )
                    {
                        do
                        {
                            i--;
                        }while(connectBoard[i][j] == 'x' || connectBoard[i][j] == 'o');
                        connectBoard[i][j] = 'o';
                        if( i == -1)
                        {
                            printf("***Bad entry, try again: ");
                            scanf("%d", &spot);
                            j = spot - 1;
                            i = 5;
                            connectBoard[i][j] = 'o';
                        }
                    }
                    turn++;
                }
                break;
            }
            printf("\n");
            for( i = 0; i < 6; i++)// prints out 2D array board
            {
                for( j = 0; j < 7; j++)
                {
                    printf("%c", connectBoard[i][j]);
                }
                printf("\n");
            }
            printf("=======\n");
            printf("1234567\n");
        }

    }while( spot != 0 );




    return 0;
}

Why do while? Use a simple While in a function an do a return or break. In my opinion do while should be avoid as much as possible. And please stop using printf like this, this is awfull, buffering etc.... read printf man :) — pix
– pix, Commented Sep 30, 2016 at 9:23
j = spot - 1; when spot is 0 address the matrix out of bound, so UB. — LPs
– LPs, Commented Sep 30, 2016 at 9:24
BTW the printf that ask for 0 to exit is inside a double for loop. You must exits both to kill the external while loop. — LPs
– LPs, Commented Sep 30, 2016 at 9:25
This code is needlessly complex. You should break it down into functions. As a side-effect, that will probably cause most problems to go away. — Lundin
– Lundin, Commented Sep 30, 2016 at 9:40
The do-while loop is hard to follow since it contains so many statements. Define a function for "player turn" and call it for each player. That way you also avoid code duplication. — August Karlstrom
– August Karlstrom, Commented Sep 30, 2016 at 9:40

user5478656 · Accepted Answer · 2016-09-30 09:43:24Z

1

After reading the spot variable, you can check if the value is 0 and break:

   printf(" Player %c, drop your piece in which column (1-7 or 0 to quit): ", player2);
   scanf("%d", &spot);
   if (spot == 0)
     return 1;
   j = spot - 1;

and change your do while to a while loop to avoid confusion.

edited Sep 30, 2016 at 9:43

answered Sep 30, 2016 at 9:32

user5478656

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1 Comment

user5478656 Over a year ago

ah yes, in that case we can exit.

AFR · Accepted Answer · 2016-09-30 09:27:13Z

0

Use a variable only for that loop. You are using spot inside your loop to do other things, use it only for the while purpose.

Then, you know the diference between do/while and while? I dont understand very well your program, but if you are reading a spot, you can read it at beggining and outside the loop and then check it with a while loop. Its the same but maybe its more easy for you.

answered Sep 30, 2016 at 9:27

AFR

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2 Comments

Nico Over a year ago

ok, so I see what you mean by using a different variable for the while loop, but then how would the user choose 0 to quit? If I'm understanding right, I think I may have tried that already. I made another variable called end, then set it to equal whatever the user input for spot, and used just a while loop to see if end was equal to 0, which also didn't work for me. Its a program to play connect 4.

AFR Over a year ago

Then why if the player enter 0 you dont turn end into the while exit condition?

user6731023 · Accepted Answer · 2016-09-30 09:35:31Z

0

Why are you using spot for while loop. as per C language, It stores a garbage value.

Even if you use, please do not set values to it. Please check basic C variables declaration.

answered Sep 30, 2016 at 9:35

user6731023

1 Comment

LPs Over a year ago

Mainly right, but in this specific case the loop is a do-while, so spot is inited by internal loops.

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