矩阵相关

Given a screen with all pixels having one of two colors. Now I will click on a random pixel.
Then that pixel & all the adjacent pixels with same color should change the color to the second color.

adjacent = vertically or horizontally above or blow.

package com.zhuyu_deng.test;

public class Test
{

	private static void printMatrix(char[][] a)
	{
		for (int i = 0; i < a.length; ++i)
		{
			for (int j = 0; j < a[i].length; ++j)
			{
				System.out.print(a[i][j] + "  ");
			}
			System.out.println();
		}
	}
//	关于FloodFill算法的解释
//	以下就是源程序 事实上就是广度搜索
//	但是必须要建立一个所谓的方向数组
	private static void floodFill(char[][] a, int x, int y)
	{
		class Node
		{
			public Node(int x, int y)
			{
				this.x = x;
				this.y = y;
			}
			int x;
			int y;
		}

		int px[] = new int[] {0, 0, -1, 1};
		int py[] = new int[] {-1, 1, 0, 0};
		char orgColor = a[x][y];
		char revColor = a[x][y] == 'W' ? 'B' : 'W';
		int size = 0;
	
		Node stack[] = new Node[a.length * a[0].length];
		stack[size] = new Node(x, y);
		while (size >= 0)
		{
			Node cur = stack[size];
			size--;
			a[cur.x][cur.y] = revColor;
			
			for (int i = 0; i < 4; ++i)
			{
				int xx = cur.x + px[i];
				int yy = cur.y + py[i];
				if (xx >= 0 && xx < a.length && yy >= 0 && yy < a[0].length)
				{
					if (a[xx][yy] == orgColor)
						stack[++size] = new Node(xx, yy);
				}
			}
			
		}
		
	}

	public static void main(String args[])
	{
		char a[][] = new char[][] { { 'W', 'B', 'W', 'W', 'B', 'W' },
				{ 'B', 'B', 'W', 'W', 'B', 'W' },
				{ 'W', 'B', 'B', 'B', 'W', 'B' },
				{ 'W', 'B', 'W', 'W', 'B', 'B' } };
		
		
		printMatrix(a);
		floodFill(a, 2, 2);

		System.out.println();
		printMatrix(a);
		
	}
}

Edit: Question seem to be not clear to some ppl. Giving an ex:

Given below & clicked on 2nd row, 2nd col
W B W W B W
B B W W B W
W B B B W B
W B W W B B

Covert to
W W W W B W
W W W W B W
W W W W W B
W W W W B B

package com.zhuyu_deng.test;

import java.util.Stack;

public class Test
{

	private static void printMatrix(char[][] a)
	{
		for (int i = 0; i < a.length; ++i)
		{
			for (int j = 0; j < a[i].length; ++j)
			{
				System.out.print(a[i][j] + "  ");
			}
			System.out.println();
		}
	}
	
	private static void floodFill(char[][] a, int x, int y)
	{
		class Node
		{
			public Node(int x, int y)
			{
				this.x = x;
				this.y = y;
			}

			int x;
			int y;
		}

		char orgColor = a[x][y];
		char revColor = a[x][y] == 'W' ? 'B' : 'W';
		int size = 0;
	
		Node stack[] = new Node[a.length * a[0].length];
		stack[size] = new Node(x, y);
		while (size >= 0)
		{
			Node cur = stack[size];
			size--;
			a[cur.x][cur.y] = revColor;
			if (cur.x - 1 >= 0 && orgColor == a[cur.x - 1][cur.y])
			{
				stack[++size] = (new Node(cur.x-1, cur.y));
			}
			if (cur.x + 1 < a.length && orgColor == a[cur.x + 1][cur.y])
			{
				stack[++size] = (new Node(cur.x+1, cur.y));
			}
			if (cur.y - 1 >= 0 && orgColor == a[cur.x][cur.y - 1])
			{
				stack[++size] = (new Node(cur.x, cur.y-1));
			}
			if (cur.y + 1 < a[0].length && orgColor == a[cur.x][cur.y + 1])
			{
				stack[++size] = (new Node(cur.x, cur.y + 1));
			}
		}
		
	}

	public static void main(String args[])
	{
		// int[] a = {-2,11,-4,13,-5,-2};
		int[][] b = { { 0, -2, -7, 0 }, { 9, 2, -6, 2 }, { -4, 1, -4, 1 },
				{ -1, 8, 0, -2 } };
		int[][] matrix = { { 2, 3, 4, 1 }, { 1, 1, 3, 9 }, { 2, 2, 3, 1 },
				{ 2, 2, 3, 1 } };
		char a[][] = new char[][] { { 'W', 'B', 'W', 'W', 'B', 'W' },
				{ 'B', 'B', 'W', 'W', 'B', 'W' },
				{ 'W', 'B', 'B', 'B', 'W', 'B' },
				{ 'W', 'B', 'W', 'W', 'B', 'B' } };
		
		
		printMatrix(a);

		floodFill(a, 2, 2);

		System.out.println();

		printMatrix(a);
		
	}
}