Connect Four C++ - c++

Question

I am coding the game connect four for my computer science class, everything was going great then I dont know what happened but I kept getting Sementation faults whenever I tried to run it. Here is my code.
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cctype>
using namespace std;
struct game{
char **board;
char p1;
char p2;
};
void print_board(game p, int r, int c);
bool play(game p, bool gamewon, int r, int c, int pieces);
bool check(int a, int b, game p, int r, int c, int pieces);
int drop(int b, char player, game p, int c);
int main(int argc, char *argv[]){
game p;
int r, c, pieces;
bool gamewon = false;
/*if(argc == 7) {
for(int i = 1; i < argc; i += 2) {
if(argv[i][0]=='-' && argv[i][1]=='r')
r = atoi(argv[i+1]);
else if(!strcmp(argv[i],"-c"))
c = atoi(argv[i+1]);
else if(!strcmp(argv[i],"-p")){
pieces = atoi(argv[i+1]);
while (pieces < 1){
cout << "You cannot have 0 pieces to connect." << endl;
cout << "Please enter a positive, non-zero integer"
<< " for the number of pieces to connect: ";
cin >> pieces;
}
}
else
cout << "Error." << endl;
}
}*/
r = 6;
c = 7;
pieces = 4;
p.board = new char*[r];
for(int i=0; i < r;i++)
p.board[i] = new char[c];
for(int a =0; a < r; a++){
for(int b = 0; b < c; b++)
p.board[a][b] = ' ';
}
print_board(p, r, c);
gamewon = play(p, gamewon, r, c, pieces);
return 0;
}
bool play(game p, bool gamewon, int r, int c, int pieces){
int col, hold = 0, charsPlaced = 0;
char player = 'y';
while(!gamewon){
if(hold != -1){
if(player =='y'){
cout<<"Player 1, what column do you want to put your piece? ";
player = 'r';
}
else{
cout<<"Player 2, what column do you want to put your piece? ";
player = 'y';
}
}
while(true){
if(charsPlaced == r*c) break;
cin>>col;
col--;
if(col <=r && col>= 0) break;
else cout<< "\nPlease enter a value between 1 and " << c << ": ";
if (cin.fail()){
cin.clear();
char d;
cin>>d;
}
}
if(charsPlaced == r*c) break;
hold = drop(col,player, p, c);
if(hold == -1) cout<<"Column is full!\nPlease enter another number between 1 and " << c << ": ";
else{
gamewon = check(hold, col, p, r, c, pieces);
charsPlaced ++;
print_board(p, r, c);
}
}
if(charsPlaced == r*c){
cout<<"No winner! Game is a draw\n";
return true;
}
if(player == 'y')
cout<<"Player 2 is the winner!\n";
else cout<<"Player 1 is the winner!\n";
return true;
}
void print_board(game p, int r, int c){
cout << endl;
for(int a = 0; a < r; a++){
for(int b = 0; b < c; b++)
cout << "|" << p.board[a][b];
cout << "|";
cout << endl;
for(int i = 0; i < c; i++)
cout << "--";
cout << endl;
}
}
bool check(int a, int b, game p, int r, int c, int pieces){
int vertical = 1, horizontal = 1, diagonalone = 1, diagonaltwo = 1, i , j;
cout << i << " " << b << " " << a << endl;
char player = p.board[a][b];
cout << player << endl;
for(i = a + 1; p.board[i][b] == player && i < r; i++, vertical++);
for(i = a - 1; p.board[i][b] == player && i >= 0; i--, vertical++);
if(vertical >= pieces)
return true;
for(j = b - 1; p.board[a][j] == player && j >= 0; j--, horizontal++);
for(j = b + 1; p.board[a][j] == player && j < c; j++, horizontal++);
if(horizontal >= pieces)
return true;
for(i = a - 1, j = b - 1; p.board[i][j] == player && i >= 0 && j >= 0; diagonalone++, i--, j--);
for(i = a + 1, j = b + 1; p.board[i][j] == player && i <= r && j <= c;diagonalone++, i++, j++);
if(diagonalone >= pieces)
return true;
for(i = a - 1, j = b + 1; p.board[i][j] == player && i >= 0 && j <= c; diagonaltwo++, i--, j++);
for(i = a + 1, j = b - 1; p.board[i][j] == player && i <= r && j >= 0; diagonaltwo++, i++, j--);
if(diagonaltwo >= pieces)
return true;
return false;
}
int drop(int b, char player, game p, int c){
if(b >= 0 && b <= c){
if(p.board[0][b] == ' '){
int i;
for(i = 0; p.board[i][b] == ' '; i++)
if(i == 5){
p.board[i][b] = player;
return i;
}
i--;
p.board[i][b] = player;
return i;
}
else{
return -1;
}
}
else{
return -1;
}
}

Answer 1

You are using
char **board;
in your game struct.
But this 2D array is never allocated and yet, you are working with it.
You are missing something like this:
in C:
board = malloc(10 * sizeof(char *));
for (int i = 0; i < 10; i++)
{
board[i] = malloc(10 * sizeof(char));
}
in C++:
board = new char*[10]
for (int i = 0; i < 10; i++)
{
board[i] = new char[10];
}

Answer 2

For starters, if you are in a Linux environment, valgrind is very helpful in finding where your segmentation fault is. To use it, if your program is called hello, just run it as valgrind hello.
Another method to debug these is to put cout or printf statements throughout your code, and observe what the last output was. You are probably indexing beyond the end of an array. Keep in mind that if you declare int x[5], the valid index values are 0 to 4.
You will probably need to change your for loops to < vs. <= so you aren't reading past the last part of the board (keep in mind that arrays are 0 indexed in c++).