import java.util.Scanner;
public class Connect4 {
	public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);
		char board[][] = new char[6][7];
		int spacesLeft[][] = new int[1][7];
		int turn=1;
		int selection;
		char playerSymbol;
		String winner = "";
		//Declares board and sets all values to a space (placeholder)
		for(int x=0;x<board.length;x++) {
			for(int y=0;y<board[0].length;y++) {
				board[x][y] = ' ';
			}
		}
		//Sets all the spaces left to 6
		for(int z=0;z<=board[0].length-1;z++) {
			spacesLeft[0][z] = 5;
		}
		//Get the player's name
		System.out.print("Player 1\'s name? ");
		String player1 = reader.nextLine();
		System.out.print("Player 2\'s name? ");
		String player2 = reader.nextLine();
		//Main Program loops
		do {
			//Assign the player Symbol
			if (turn == 1) { playerSymbol = 'R'; }
			else { playerSymbol = 'B'; }
			//Displays the player turn and the board
			System.out.println("Player "+turn+"\'s turn.");
			for(int x=0;x<board.length;x++) {
				for(int y=0;y<board[0].length;y++) {
					System.out.print(board[x][y] +" | ");
				}
				System.out.println("\n--------------------------");
			}
			//Loop to get player's column selection
			do {
				System.out.print("What column do you want to place your chip in? ");
				selection = reader.nextInt();
				//In the following lines, placement of the conditionals is crucial because
				//if the array condition comes before the conditional to verify the column
				//the program will exit with an error.
				if (selection > 7 || selection < 0)
					System.out.println("Invalid column selection, try again.");
				else if(spacesLeft[0][selection-1] == -1) 
					System.out.println("Column is full, try again.");
			} while(selection > 7 || selection < 0 || spacesLeft[0][selection-1] == -1);
			//Replace the space with the symbol & subtract an open space from that column.
			board[spacesLeft[0][selection-1]] [selection-1] = playerSymbol;
			spacesLeft[0][selection-1] = spacesLeft[0][selection-1]-1;
			
			//Check for a win
			if(getWinner(board))
				winner = ""+turn;
			
			//Switch the turns
			if (turn == 1) {turn = 2;}
			else { turn = 1; }
		}while(winner.equals(""));
	}
	
	/**
	 * Helper function to see if there are any winners. 
	 * Checks the / diagonal.
	 */
	private boolean checkDiag1(int x, int y, char grid[][]) {
		int i;
		
		if((x > 3) || (y > 2)) 
			return false;
		
		int player = grid[x][y];
		int count = 1;
		
		for(i = 1;i < 4;i++) {
			if(grid[x+i][y+i] == player) 
				count++; 
			else 
				break;
		}
		return (count==4);
	}
	/*
	* Helper function to see if there are any winners. 
	* Checks the \ diagonal.
	*/
	private boolean checkDiag2(int x, int y, char grid[][]) {
		int i;
		if((x < 3) || (y > 2)) 
			return false;
		
		int player = grid[x][y];
		int count = 1;
		
		for(i = 1;i < 4;i++) {
			if(grid[x-i][y+i] == player)
				count++;
			else 
				break;
		}
		return (count==4);
	}
	/*
	* Helper function to see if there are any winners. 
	* Checks horizontally.
	*/
	private boolean checkHorizontal( int x, int y, char grid[][]) {
		int i;
		
		if(x > 3) 
			return false;
		int player = grid[x][y];
		int count = 1;
		
		for(i = (x+1);i < (x+4);i++) {
			if( grid[i][y] == player ) 
				count++; 
			else 
				break;
		}
		return (count==4);
	}
	
	/*
	* Helper function to see if there are any winners. 
	* Checks vertically.
	*/
	private boolean checkVertical(int x, int y, char grid[][]) {
		int i;
		
		if(y > 2) 
			return false;
		
		int player = grid[x][y];
		int count = 1;
		
		for(i = (y+1);i < (y+4);i++) {
			if(grid[x][i] == player) 
				count++; 
			else 
					break;
		}
		return (count==4);
	}
	
	/*
	* Determines if anyone has won the game in the Board's current state.
	*/
	public int getWinner(char grid[][]) {
		int x, y;
		int winner = 0;
		
		for(y = 0; y < 6;y++) {
			for(x = 0; x < 7;x++) {
				if(grid[x][y] != 0) {
					if(checkHorizontal(x,y,grid) || checkVertical(x,y,grid) || checkDiag1(x,y,grid) || checkDiag2(x,y,grid)) 
					{
						winner = grid[x][y];
						break;
					}
				}
			}
			if(winner != 0) break;
		}
	
		if(winner == 0) {
			for(x = 0; x < 7; x++) {
				if(grid[x][5] == 0) { 
					winner = -1;
					break; 
				}
			}
		}	
		return winner;
	}
}