UVa 00339 - SameGame Simulation (follow problem description)

Link:https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=5&page=show_problem&problem=275
Sol:

import java.util.Scanner;
	import java.io.*;
	class Board {
	public int m, n;
	int map[][];
	int colum[];
	int columLen;
	public Board(int m, int n) {
	this.m = m;
	this.n = n;
	map = new int[m][n];
	for (int i = 0; i < m; i++)
	for (int j = 0; j < n; j++)
	map[i][j] = -1;
	colum = new int[n];
	for (int i = 0; i < n; i++)
	colum[i] = m;
	columLen = n;
	}
	public int getItem(int x, int y) {
	return map[x][y];
	}
	public void setItem(int x, int y, int item) {
	map[x][y] = item;
	}
	private boolean isOnTheBoard(int i, int j) {
	return i >= 0 && j >= 0 && i < m && j < n;
	}
	@Override
	public String toString() {
	//int max = 0;
	//for (int i = 0; i < columLen; i++)
	//if (colum[i] > max)
	//max = colum[i];
	StringBuilder builder = new StringBuilder();
	for (int i = 0; i < m; i++) {
	builder.append(" ");
	for (int j = 0; j < n; j++) {
	builder.append((map[m - i - 1][j] == -1?" ":map[m-i-1][j]) + (j < (n-1)?" ":""));
	}
	builder.append("\n");
	}
	return builder.toString();
	}
	public void removeRegion(int x, int y) {
	//for (int i = 0; i < columLen; i++) {
	// System.out.print(colum[i] + " ");
	//}
	//System.out.println();
	if (isValidRegion(x, y)) {
	boolean compress = removeCells(x, y, map[x][y]);
	//System.out.println("Remove");
	//System.out.println(this);
	compressRows();
	//System.out.println("c rows: ");
	//System.out.println(this);
	if (compress) { // if after this removal there are no items inside some colum
	//System.out.println("Compress col");
	compressColums();
	}
	}
	}
	private boolean removeCells(int x, int y, int value) {
	if (!isOnTheBoard(x, y) || map[x][y] != value)
	return false;
	boolean result = false;
	map[x][y] = -1;
	if (--colum[y] == 0) { // now we have one less number in this colm
	//System.out.println("No more items inside colum");
	result = true; // if no items left in coulum, do the copress of colums
	}
	result = removeCells(x-1, y, value) || result;
	result = removeCells(x+1, y, value) || result;
	result = removeCells(x, y-1, value) || result;
	result = removeCells(x, y+1, value) || result;
	return result;
	}
	private boolean isValidRegion(int x, int y) {
	if (!isOnTheBoard(x, y))
	return false;
	if (map[x][y] == -1)
	return false;
	// Check if there is one more number same as one on x, y in the connected cells
	// this is to check if reagon has at least 2 elements.
	if (isOnTheBoard(x-1, y) && map[x-1][y] == map[x][y])
	return true;
	if (isOnTheBoard(x+1, y) && map[x+1][y] == map[x][y])
	return true;
	if (isOnTheBoard(x, y-1) && map[x][y-1] == map[x][y])
	return true;
	if (isOnTheBoard(x, y+1) && map[x][y+1] == map[x][y])
	return true;
	//This is reagon with single value
	return false;
	}
	private void compressColums() {
	int k = 0;
	for (int i = 0; i < columLen; i++) {
	if (colum[i] != 0) {
	if (i != k) {
	colum[k] = colum[i];
	//move colum
	for (int j = 0; j < m; j++) {
	map[j][k] = map[j][i];
	map[j][i] = -1;
	}
	}
	k++;
	}
	}
	columLen = k;
	}
	private void compressRows(){
	for (int j = 0; j < columLen; j++) {
	if (colum[j] == 0)
	continue;
	int k = 0;
	for (int i = 0; i < m; i++) {
	if (map[i][j] != -1) {
	if (i != k) {
	map[k][j] = map[i][j];
	map[i][j] = -1;
	}
	k++;
	}
	}
	}
	}
	}
	public class Main {
	public static void main(String[] args) throws Exception {
	Scanner in = new Scanner(System.in);
	String line;
	int tc = 0, m, n;
	while (true) {
	m = in.nextInt();
	n = in.nextInt();
	if (m == 0 || n == 0)
	break;
	if (++tc != 1) {
	System.out.println();
	}
	Board board = new Board(m, n);
	for (int i = 0; i < m; i++) {
	for (int j = 0; j < n; j++) {
	board.setItem(i, j, in.nextInt());
	}
	}
	System.out.println("Grid " + tc + ".");
	//System.out.println(board);
	int x, y;
	while (true) {
	x = in.nextInt();
	y = in.nextInt();
	if (x == 0 && y == 0)
	break;
	//System.out.println("Move: " + (x-1) + " " + (y-1));
	board.removeRegion(x-1, y-1);
	//System.out.println("After move");
	//System.out.println(board);
	}
	if (board.columLen != 0) {
	System.out.print(board);
	}
	else
	System.out.println(" Game Won");
	}
	}
	}