Weird output on TicTacToe game written in C-CodePudding

I am a beginner C programmer and while writing a tictactoe game in C, I encountered a strange output. I mainly used if statements to check if the "squares" are either 'X' or 'O'

#include <stdio.h>

int main(){
    int p1,p2;
    char arr[] = {'1','2','3','4','5','6','7','8','9'};
    void drawboard(){
        printf("%c|%c|%c\n",arr[0],arr[1],arr[2]);
        printf("-----\n");
        printf("%c|%c|%c\n",arr[3],arr[4],arr[5]);
        printf("-----\n");
        printf("%c|%c|%c\n",arr[6],arr[7],arr[8]);
    }
    while(1>0){
        drawboard();
        printf("Player 1, enter your choice:\n");
        scanf("%d",&p1);
        printf("Player 2, enter your choice:\n");
        scanf("%d",&p2);
        arr[p1-1] = 'X';
        arr[p2-1] = 'O';
        if(arr[0]&&arr[1]&&arr[2]=='X'){
            printf("Player 1 won.\n");
            return 1;

        }
        if(arr[3]&&arr[4]&&arr[5]=='X'){
            printf("Player 1 won.\n");
            return 1;
        }
        if(arr[6]&&arr[7]&&arr[8]=='X'){
            printf("Player 1 won.\n");
            return 1;
        }
        if(arr[0]&&arr[3]&&arr[6]=='X'){
            printf("Player 1 won.\n");
            return 1;
        }
        if(arr[1]&&arr[4]&&arr[7]=='X'){
            printf("Player 1 won.\n");
            return 1;
        }
        if(arr[2]&&arr[5]&&arr[8]=='X'){
            printf("Player 1 won.\n");
            return 1;
        }
        if(arr[0]&&arr[4]&&arr[8]=='X'){
            printf("Player 1 won.\n");
            return 1;
        }
        if(arr[2]&&arr[4]&&arr[6]=='X'){
            printf("Player 1 won.\n");
            return 1;
        }
        else if(arr[0]&&arr[1]&&arr[2]=='O'){
            printf("Player 2 won.\n");
            return 1;
        }
        else if(arr[3]&&arr[4]&&arr[5]=='O'){
            printf("Player 2 won.\n");
            return 1;
        }
        else if(arr[6]&&arr[7]&&arr[8]=='O'){
            printf("Player 2 won.\n");
            return 1;
        }
        else if(arr[0]&&arr[3]&&arr[6]=='O'){
            printf("Player 2 won.\n");
            return 1;
        }
        else if(arr[1]&&arr[4]&&arr[7]=='O'){
            printf("Player 2 won.\n");
            return 1;
        }
        else if(arr[2]&&arr[5]&&arr[8]=='O'){
            printf("Player 2 won.\n");
            return 1;
        }
        else if(arr[0]&&arr[4]&&arr[8]=='O'){
            printf("Player 2 won.\n");
            return 1;
        }
        else if(arr[2]&&arr[4]&&arr[6]=='O'){
            printf("Player 2 won.\n");
            return 1;
        }
        else{
            continue;
        }

    }
    return 0;
}

After the first and the second player's input, if the input is '8' or '6', it says he won, even if only one space was occupied.

CodePudding user response：

You wrote:

arr[6]&&arr[7]&&arr[8]=='X'

which means:

if arr[6] is true and arr[7] is true and arr[8]=='X' is true.

True means any character except '\0', so all the squares are true and this condition is true as soon as arr[8] is an X.

You meant:

arr[6]=='X' && arr[7]=='X' && arr[8]=='X'

(spaces are optional) which checks that all 3 of them are X. And you have to fix all the if statements this way.

CodePudding user response：

Prefaced by my top comments. A few issues ...

Don't use nested functions
Put arr at global scope.
if syntax is incorrect. (e.g.) if(arr[0]&&arr[1]&&arr[2]=='X') should be if ((arr[0] == 'X') && (arr[1] == 'X') && (arr[2] == 'X'))
No check for illegal moves or out of range moves.
Not all possible win positions checked (e.g. missing a diagonal).
No need for separate win check for each player. A win [for either player] is all three in a given direction match.
The program can be greatly simplified with breakup into smaller functions.

Here is the corrected code. It is annotated.

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

char arr[] = { '1', '2', '3', '4', '5', '6', '7', '8', '9' };

void
drawboard(void)
{
    printf("%c|%c|%c\n", arr[0], arr[1], arr[2]);
    printf("-----\n");
    printf("%c|%c|%c\n", arr[3], arr[4], arr[5]);
    printf("-----\n");
    printf("%c|%c|%c\n", arr[6], arr[7], arr[8]);
}

// match3 -- decide if win
// RETURNS: winning char or zero
int
match3(int a,int b,int c)
{
    int x;

    --a;
    --b;
    --c;

    x = arr[a];

    return ((arr[b] == x) && (arr[c] == x)) ? x : 0;
}

// check -- check for win
int
check(void)
{
    int win;

    do {
        // top row
        win = match3(1,2,3);
        if (win)
            break;

        // middle row
        win = match3(4,5,6);
        if (win)
            break;

        // bottom row
        win = match3(7,8,9);
        if (win)
            break;

        // left column
        win = match3(1,4,7);
        if (win)
            break;

        // middle column
        win = match3(2,5,8);
        if (win)
            break;

        // right column
        win = match3(3,6,9);
        if (win)
            break;

        // left to right diagonal
        win = match3(1,5,9);
        if (win)
            break;

        // right to left diagonal
        win = match3(3,5,7);
        if (win)
            break;
    } while (0);

    switch (win) {
    case 'X':
        printf("Player 1 won.\n");
        break;
    case 'O':
        printf("Player 2 won.\n");
        break;
    }

    if (win)
        drawboard();

    return win;
}

// legal -- check for remaining legal moves
void
legal(void)
{
    int more;

    // look for remaining legal moves
    more = 0;
    for (int idx = 0;  idx < 9;    idx) {
        more = (arr[idx] != 'X') && (arr[idx] != 'O');
        if (more)
            break;
    }

    if (! more) {
        printf("No more legal moves -- no winner\n");
        drawboard();
        exit(0);
    }
}

// ask -- ask player for moves
int
ask(int playno,int x)
{
    char buf[100];
    char *cp;
    int move;

    printf("\n");
    legal();

    while (1) {
        drawboard();

        printf("Player %d, enter your choice:\n",playno);
        if (fgets(buf,sizeof(buf),stdin) == NULL) {
            printf("EOF\n");
            exit(0);
        }

        // echo for debug input from file
        do {
            struct termios tio;
            if (tcgetattr(fileno(stdin),&tio) < 0)
                fputs(buf,stdout);
        } while (0);

        // get the move
        move = strtol(buf,&cp,10);

        if (*cp != '\n') {
            printf("syntax error\n");
            continue;
        }

        // move is within bounds
        if ((move >= 1) && (move <= 9)) {
            --move;

            // check for move to an already occupied space
            if ((arr[move] == 'X') || (arr[move] == 'O')) {
                printf("already has an '%c'\n",arr[move]);
                continue;
            }

            // make the move
            arr[move] = x;
            break;
        }

        printf("move out of range\n");
    }

    return check();
}

int
main(void)
{
    int more;

    while (1) {
        if (ask(1,'X'))
            break;
        if (ask(2,'O'))
            break;
    }

    return 0;
}

Below are some sample games I used to test the program ...


1|2|3
-----
4|5|6
-----
7|8|9
Player 1, enter your choice:
1

X|2|3
-----
4|5|6
-----
7|8|9
Player 2, enter your choice:
4

X|2|3
-----
O|5|6
-----
7|8|9
Player 1, enter your choice:
2

X|X|3
-----
O|5|6
-----
7|8|9
Player 2, enter your choice:
5

X|X|3
-----
O|O|6
-----
7|8|9
Player 1, enter your choice:
3
Player 1 won.
X|X|X
-----
O|O|6
-----
7|8|9


1|2|3
-----
4|5|6
-----
7|8|9
Player 1, enter your choice:
1

X|2|3
-----
4|5|6
-----
7|8|9
Player 2, enter your choice:
4

X|2|3
-----
O|5|6
-----
7|8|9
Player 1, enter your choice:
2

X|X|3
-----
O|5|6
-----
7|8|9
Player 2, enter your choice:
5

X|X|3
-----
O|O|6
-----
7|8|9
Player 1, enter your choice:
3
Player 1 won.
X|X|X
-----
O|O|6
-----
7|8|9


1|2|3
-----
4|5|6
-----
7|8|9
Player 1, enter your choice:
1

X|2|3
-----
4|5|6
-----
7|8|9
Player 2, enter your choice:
2

X|O|3
-----
4|5|6
-----
7|8|9
Player 1, enter your choice:
3

X|O|X
-----
4|5|6
-----
7|8|9
Player 2, enter your choice:
4

X|O|X
-----
O|5|6
-----
7|8|9
Player 1, enter your choice:
5

X|O|X
-----
O|X|6
-----
7|8|9
Player 2, enter your choice:
9

X|O|X
-----
O|X|6
-----
7|8|O
Player 1, enter your choice:
8

X|O|X
-----
O|X|6
-----
7|X|O
Player 2, enter your choice:
7

X|O|X
-----
O|X|6
-----
O|X|O
Player 1, enter your choice:
6

No more legal moves -- no winner
X|O|X
-----
O|X|X
-----
O|X|O