How can I fix my C++ Connect4 checkGameOver Function - c++

Question

We have to make Connect4 in C++ as our last assignment for one of my classes. As of right now I have a fairly functional version. I had a really promising idea for a recursive solution for checking if the game is over but the issue is it only checks starting from the token it is starting at. For example if the most recently placed token has 3 of the same kind in any direction that is valid it works, but if it has 2 in one direction and 1 the opposite way it doesn't work. Does anyone have any ideas for how I could edit my function to incorporate the 2nd situation or should I just scrap it and rewrite it differently. Here is my code.
//TODO implement checking spots other than start
#include <iostream>
#include <string>
#include <ctime>
#include <cstdlib>
int runGame(int, int, int);
void promptUser(int**, int[], int, int, int);
void genRanMove(int**, int[], int, int);
bool checkGameOver(int**, int, int, int, int, int, int, int, int);
void showBoard(int**, int, int);
void playAgain();
using namespace std;
int main(int argc, char *argv[]) {
if (argc < 4) {
cerr << "Not enough input, syntax is 1/2 players, # columns, and # of rows" << endl;
exit(0);
}
if (argc == 4 && (argv[1][0] == '1' || argv[1][0] == '2') && (argv[2][0] >= '1' && argv[2][0] <= '9') && (argv[3][0] >= '1' && argv[3][0] <= '9')) {
cout << "\n\nYou have chosen to play Connect 4 in " << argv[1][0] << " player mode and with " << argv[2][0] << " columns and with " << argv[3][0] << " rows.\n" << endl;
}
else {
cerr << "Improper syntax, syntax is 1/2 players, # columns, and # of rows" << endl;
exit(0);
}
cout << "Welcome to Connect 4, each player will take a turn choosing a column to select, a metaphorical coin will fall down to the highest availible row.\nThe game ends when a player has gotten 4 of their coins in a row horizontally, vertically, or diagonally.\nPlayer 1 will always use 1's and Player 2 will always be 2's.\nThe AI will always be 3's.\nEmpty slots will be shown as 0's.\n\n" << endl;
srand(time(NULL));
int winner = runGame(argv[1][0] - '0', argv[2][0] - '0', argv[3][0] - '0');
if (winner == 1 || winner == 2) {
cout << "Winner was player # " << winner << endl;
}
else if (winner == 3)
cout << "You let the AI win :(" << endl;
else if (winner == -1)
cout << "The game ended in a tie" << endl;
playAgain();
}
/******************************************************
** Function: runGame
** Description: runsGame
** Parameters: gameMode columns rows
** Pre-Conditions:
** Post-Conditions: returns winning player, 1 or 2 for player # and 3 for ai
******************************************************/
int runGame(int gameMode, int columns, int rows) { //returns which player won
int holdPoints[2] = { 0, 0 };
switch (gameMode) {
case 1:
cout << "You have chosen to play against an AI" << endl;
break;
case 2:
cout << "You have chosen to play with another human player" << endl;
break;
}
int** board = new int*[columns];
for (int i = 0; i< columns; i++) {
board[i] = new int[rows];
}
for (int i = 0; i< columns; i++) {
for (int j = 0; j< rows; j++) {
board[i][j] = 0;
}
}
for (int i = 0; i< rows*columns/2; i++) { //check for number of possible moves in order to have a tie
showBoard(board, rows, columns);
promptUser(board, holdPoints, rows, columns, 1);
if (checkGameOver(board, holdPoints[0], holdPoints[1], 0, 1, 0, 1, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 1, 1, 0, 1, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 1, 0, 0, 1, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 0, -1, 0, 1, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], -1, -1, 0, 1, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], -1, 0, 0, 1, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 1, -1, 0, 1, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], -1, 1, 0, 1, rows, columns)) {
return 1;
}
cout << "\n\n";
showBoard(board, rows, columns);
if (gameMode == 2) {
promptUser(board, holdPoints, rows, columns, 2);
if (checkGameOver(board, holdPoints[0], holdPoints[1], 0, 1, 0, 2, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 1, 1, 0, 2, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 1, 0, 0, 2, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 0, -1, 0, 2, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], -1, -1, 0, 2, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], -1, 0, 0, 2, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 1, -1, 0, 2, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], -1, 1, 0, 2, rows, columns)) {
return 2;
}
}
else if (gameMode == 1) {
genRanMove(board, holdPoints, rows, columns);
if (checkGameOver(board, holdPoints[0], holdPoints[1], 0, 1, 0, 3, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 1, 1, 0, 3, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 1, 0, 0, 3, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 0, -1, 0, 3, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], -1, -1, 0, 3, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], -1, 0, 0, 3, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], 1, -1, 0, 3, rows, columns) || checkGameOver(board, holdPoints[0], holdPoints[1], -1, 1, 0, 3, rows, columns)) {
return 3;
}
}
//showBoard(board, rows, columns);
cout << "\n\n";
}
for (int i = 0; i < columns; i++) {
delete[] board[i];
}
delete[] board;
return -1; //signifies a tie
}
/******************************************************
** Function: promptUser
** Description: gets input from user for their turn, stores the resting place of their token in points
** Parameters: board and array to hold point,num columns
** Pre-Conditions:
** Post-Conditions:
******************************************************/
void promptUser(int** board, int point[], int numRows, int numColumns, int playerNum) {
int col, lowZero;
lowZero = -1;
cout << "What column would you like to choose" << endl;
cin >> col;
if (col<0 || col > numColumns -1) {
cout << "The # you chose must be >=0 and <= " << numColumns-1 << endl;
promptUser(board, point, numRows, numColumns, playerNum);
}
//now need to find the lowest possible row in the given column that has a 0
for (int i = 0; i < numRows; i++) {
if (board[col][i] == 0)
lowZero = i;
}
if (lowZero != -1) {
board[col][lowZero] = playerNum;
cout << "Player " << playerNum << " dropped a token in column " << col << " that rested at row " << lowZero << endl;
point[0] = col;
point[1] = lowZero;
return;
}
else {
cout << "Column " << col << " was full, please pick a new one" << endl;
promptUser(board, point, numRows, numColumns, playerNum);
}
}
/******************************************************
** Function: genRanMove
** Description: gets random column from "ai", stores the resting place of their token in points
** Parameters: board and array to hold point
** Pre-Conditions:
** Post-Conditions:
******************************************************/
void genRanMove(int** board, int point[], int numRows, int numColumns) {
cout << "AI is finding a column" << endl;
int col = rand() % numColumns;
int lowZero = -1;
for (int i = 0; i < numRows; i++) {
if (board[col][i] == 0)
lowZero = i;
}
if (lowZero != -1) {
board[col][lowZero] = 3;
cout << "AI dropped a token in column " << col << " that rested at row " << lowZero << endl;
point[0] = col;
point[1] = lowZero;
return;
}
//didnt find a row that works
genRanMove(board, point, numRows, numColumns);
}
/******************************************************
** Function: showBoard
** Description: prints he current gameboard
** Parameters: the board, numrows and numcolumns
** Pre-Conditions:
** Post-Conditions:
******************************************************/
void showBoard(int** board, int numRows, int numColumns) {
for (int i = 0; i < numColumns; i++) {
for (int j = 0; j < numRows; j++) {
cout << board[j][i] << " ";
}
cout << endl;
}
}
/******************************************************
** Function: playAgain
** Description: gets info to play again
** Parameters: n/a
** Pre-Conditions:
** Post-Conditions:
******************************************************/
void playAgain() {
int again;
int mode, rows, columns;
cout << "Would you like to play again? Type 1 if so." << endl;
cin >> again;
if (again) {
cout << "What mode? 1 for 1 player and 2 for 2 player" << endl;
cin >> mode;
cout << "How many rows?" << endl;
cin >> rows;
cout << "How many columns?" << endl;
cin >> columns;
if ((mode<=0 || mode >2) || rows<= 0 || columns<= 0) {
cout << "Improper inputs. Mode must be 1/2 and rows and columns must both be >0" << endl;
playAgain();
}
else {
runGame(mode, columns, rows);
}
}
}
/******************************************************
** Function: checkGameOver
** Description: checks if game is over by recursively checking spots around original
** Parameters: board, curr col, curr row, change col, change row, total found, and what number it is looking for in the board
** Pre-Conditions:
** Post-Conditions:
******************************************************/
bool checkGameOver(int** board, int currCol, int currRow, int changeCol, int changeRow, int totalFound, int numSearch, int numRows, int numColumns) {
if (totalFound == 4) //base case
return true;
if (currRow <0 || currRow >numRows - 1 || currCol<0 || currCol> numColumns - 1)
return false;
if (board[currCol][currRow] == numSearch)
totalFound++;
else
return false; // the checked index didnt contain the same # we wanted
return checkGameOver(board, currCol + changeCol, currRow + changeRow, changeCol, changeRow, totalFound, numSearch, numRows, numColumns);
}

Answer 1

... or should I just scrap it and rewrite it differently?
That's the option I'd be going for :-)
While a recursive solution may be clever, you're probably better off, for a game-space of this size, keeping the code simple and just checking every single possibility rather than trying to recurse out from the newly-populated cell(a).
You can do this in "specialist" chunks so you don't have to worry about going off the edge of the board at any point. To do this, you limit the starting cell for each type so that it ends on an edge cell of the board, something like (pseudo-code):
# Check four cells given start and direction.
def didWin(row, col, rdelta, cdelta):
# Check if start cell not populated.
if cell[row][col] == empty:
return false
# Check if any cell in sequence doesn't match.
for i = 1 to 3 inclusive:
if cell[row][col] != cell[row+rdelta*i][col+cdelta*i]:
return false
# Otherwise, it's a win
return true
def getWinner():
# Check all possible horizontals.
for row = 0 to 5 inclusive:
for col = 0 to 3 inclusive:
if didWin(row, col, 0, 1): # cdelta=1, right.
return cell[row][col]
# Check all possible verticals.
for col = 0 to 6 inclusive:
for row = 0 to 2 inclusive:
if didWin(row, col, 1, 0): # rdelta=1, down.
return cell[row][col]
# Check all right-downs.
for row = 0 to 2 inclusive:
for col = 0 to 3 inclusive:
if didWin(row, col, 1, 1): # r/cdelta=1, right-down.
return cell[row][col]
# Check all right-ups.
for row = 3 to 5 inclusive:
for col = 0 to 3 inclusive:
if didWin(row, col, 1, -1): # rdelta=1, cdelta=-1, right-up.
return cell[row][col]
# No winner.
return empty
(a) Another good reason for doing this is that, in an educational institution, they almost always value clarity of thought over cleverness. That clarity of thought will serve you well in the start of your career and, indeed, forty years into your career, such as where I am :-)