Chapter 8 Exercise 20, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

***8.20 (Game: connect four) Connect four is a two-player board game in which the players alternately drop colored disks into a seven-column, six-row vertically suspended grid, as shown below. The objective of the game is to connect four same-colored disks in a row, a col- umn, or a diagonal before your opponent can do likewise. The program prompts two players to drop a red or yellow disk alternately. In the preceding figure, the red disk is shown in a dark color and the yellow in a light color. Whenever a disk is dropped, the program redisplays the board on the console and determines the status of the game (win, draw, or continue). Here is a sample run:

import java.util.Scanner;
 
public class ProgrammingEx8_20 {
 
 public static void main(String[] args) {
  Scanner input = new Scanner(System.in);
  int[][] values = new int[6][7];
  int noOfDisk = 0;
  String s;
  int disk;
 
  do {
 
   noOfDisk++;
   if (noOfDisk % 2 == 0) {
    s = "red";
    disk = 1;
   } else {
    s = "yellow";
    disk = 2;
   }
 
   System.out.print("Drop a " + s + " disk at column (0–6):");
   int col = input.nextInt();
   for (int i = values.length - 1; i >= 0; i--) {
    if (values[i][col] == 0) {
     values[i][col] = disk;
     break;
    }
    if (i == 0)
     System.out.println("Column full. Try again.");
   }
   displayBoard(values);
 
  } while (checkBoard(values) == false && noOfDisk != 6 * 7);
   
  if(checkBoard(values)) {
   System.out.println("The " + s + " player won");
    
  }else {
   System.out.println("It is a draw.");
  }
 
 }
 
 public static void displayBoard(int[][] values) {
 
  for (int i = 0; i < values.length; i++) {
   System.out.print("|");
   for (int j = 0; j < values[i].length; j++) {
    char c;
    if (values[i][j] == 1) {
     c = 'R';
    } else if (values[i][j] == 2) {
     c = 'Y';
    } else {
     c = ' ';
    }
 
    System.out.print(c + "|");
   }
   System.out.println();
  }
 
  for (int i = 0; i <= values.length * 2; i++) {
   System.out.print("-");
  }
 
  System.out.println();
 
 }
 
 public static boolean checkBoard(int[][] values) {
 
  return checkVer(values) || checkHor(values) || checkDia(values);
 
 }
 
 public static boolean checkVer(int[][] values) {
  // Going through the array vertically
 
  for (int i = 0; i < values[0].length; i++) {
   int start = values[0][i];
   int count = 1;
   for (int j = 1; j < values.length; j++) {
    if (start == values[j][i] && start != 0) {
     count++;
    } else {
     start = values[j][i];
     count = 1;
    }
 
    if (count == 4) {
     return true;
    }
   }
  }
 
  return false;
 
 }
 
 public static boolean checkHor(int[][] values) {
 
  // Going through the array horizontally
  
  for (int i = 1; i < values.length; i++) {
   int start = values[i][0];
   int count = 1;
   for (int j = 1; j < values[i].length; j++) {
    if (start == values[i][j] && start != 0) {
     count++;
    } else {
     start = values[i][j];
     count = 1;
    }
 
    if (count == 4) {
     return true;
    }
   }
  }
 
  return false;
 
 }
 
 public static boolean checkDia(int[][] values) {
 
  // From upper left to lower right
  // Go through the row
   
  for (int i = 0; i < values.length; i++) {
   int start = values[i][0];
   int count = 1;
   for (int j = i+1, k = 1; j < values.length && k < values[0].length; j++, k++) {
    if (start == values[j][k] && start != 0) {
     count++;
    } else {
     start = values[j][k];
     count = 1;
    }
    if (count == 4) {
     return true;
    }
   }
  }
 
  // Going through the column
   
  for (int i = 0; i < values[0].length; i++) {
   int start = values[0][i];
   int count = 1;
   for (int j = i+1, k = 1; j < values[0].length && k < values.length; j++, k++) {
    if (start == values[k][j] && start != 0) {
     count++;
    } else {
     start = values[k][j];
     count = 1;
    }
 
    if (count == 4) {
     return true;
    }
   }
  }
 
  // From upper right to lower left
  // Go through the column
   
  for (int i = 0; i < values[0].length; i++) {
   int start = values[0][i];
   int count = 1;
   for (int j = 1, k = i-1; j < values.length && k >= 0; j++, k--) {
    if (start == values[j][k] && start != 0) {
     count++;
    } else {
     start = values[j][k];
     count = 1;
    }
    if (count == 4) {
     return true;
    }
   }
  }
 
  // Going through the row
   
  for (int i = 0; i < values.length; i++) {
   int start = values[i][values[i].length-1];
   int count = 1;
   for (int j = i+1, k = values[0].length-2; j < values.length && k >= 0; j++, k--) {
    if (start == values[j][k] && start != 0) {
     count++;
    } else {
     start = values[j][k];
     count = 1;
    }
    if (count == 4) {
     return true;
    }
   }
  }
   
  return false;
 
 }
}