I have a problem in my C code.

[Dontah]

So, basically this code is for a Tic Tac Toe game, I'm trying to make a Singleplayer mode where Player 1 inserts a spot number to put his X, and Player 2 uses a random number generating function and assigns his O in a random spot. Everything works fine except, Player 2's random number does not get assigned on the board.

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <time.h>
char choice, choice2, modsel;
int player = 1, winner, end = 0, counter = 0, ran_num;

char arr[3][3] = {
  {'1','2','3'},{'4','5','6'},{'7','8','9'}
};
void numgen(int rannum) {
    srand(time(NULL));
    rannum = 1 + rand() % 9;
    ran_num = rannum;
}
void printarray() {
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
            printf("|%c|", arr[i][j]);
        }
        printf("\n");
    }
}
void playingSP() {
    char letter;
    if (player == 1) {
        scanf("%c", &choice2);
        letter = 'x';
    }
    else if (player == 2) {
        numgen(ran_num);
        choice2 = ran_num;
        letter = 'o';
    }
    else {
        printf("wrong entry");
    }

    switch (choice2) {
    case '1': arr[0][0] = letter; break;
    case '2': arr[0][1] = letter; break;
    case '3': arr[0][2] = letter; break;
    case '4': arr[1][0] = letter; break;
    case '5': arr[1][1] = letter; break;
    case '6': arr[1][2] = letter; break;
    case '7': arr[2][0] = letter; break;
    case '8': arr[2][1] = letter; break;
    case '9': arr[2][2] = letter; break;
    }
    counter++;
}
void endgame() {
    for (int i = 0; i < 3; i++)
        if ((arr[i][0] == arr[i][1]) && (arr[i][1] == arr[i][2])) {
            if (arr[i][0] == 'x')
                winner = 1;
            else
                winner = 2;
            end = 1;
            return;
        }
    for (int j = 0; j < 3; j++)
        if ((arr[0][j] == arr[1][j]) && (arr[1][j] == arr[2][j])) {
            if (arr[0][j] == 'x')
                winner = 1;
            else
                winner = 2;
            end = 1;
            return;
        }
    if ((arr[0][0] == arr[1][1]) && (arr[1][1]) == arr[2][2]) {
        if (arr[0][0] == 'x')
            winner = 1;
        else
            winner = 2;
        end = 1;
        return;
    }
    if ((arr[0][2] == arr[1][1]) && (arr[1][1]) == arr[2][0]) {
        if (arr[0][2] == 'x')
            winner = 1;
        else
            winner = 2;
        end = 1;
        return;
    }
    if (counter == 8) {
        winner = 0;
        end = 1;
    }
}
int main()
{
    printarray();
    while (end != 1)
    {
        printf("player %d enter your number:", player);
        playingSP();
        printarray();
        endgame();
        if (player == 1)
            player = 2;
        else
            player = 1;
        playingSP();
    }
    if (winner == 0)
        printf("no winner\n");
    else
        printf("player %d won the game\n", winner);
    return 0;
}

[rproffitt]

The logic in playingSP is where I see this fail. There's much to be done there.

1. Why bother with else on line 30? To me you can forgo that and make your code simpler.
2. Some sort of loop for invalid choices by either player isn't evident.

[grantyp2]

I think the problem lies in your playingSP function, specifically with the switch case setup. It works when player 1 enters their selection as it is captured by scanf and is captured as a char, where as player2's selection is a random number generated by 'numgen' which sets your int varaible 'ran_num'. But the switch case is only setup to check for char '0' through to '9' (int 1 and char '1' are two different values as char '1' is resolved down to number 49 when accessed as an integer number).

To fix, I would convert the character caught by the scanf for player1 to its int equivalent and change the switch to only check int values rather than chars. Or you could add extra case statements for the int values.