拆分查找算法在FBreader中的应用

在FBreader中,有一段代码是实现了关于点击屏幕,然后选取文字的功能.

寻着足迹,发现有一个拆分查找算法.没细看,于是想想自己先模拟实现试试.

于是有如下代码:

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;

public class BinearySearch
{
	class Rect
	{
		int	startx;
		int	starty;
		int	endx;
		int	endy;
	}

	class Point
	{
		int	x;
		int	y;
	}

	@SuppressWarnings("rawtypes")
	class ComparatorRects implements Comparator
	{

		public int compare(Object arg0, Object arg1)
		{
			Rect rect1 = (Rect) arg0;
			Rect rect2 = (Rect) arg1;
			if (rect2.endy > rect1.endy)
			{
				return -1;
			}
			else
				if (rect2.endy == rect1.endy)
				{
					if (rect2.endx > rect1.endx)
					{
						return -1;
					}
					else
						if (rect2.endx < rect1.endx)
						{
							return 1;
						}
						else
						{
							return 0;
						}
				}
				else
				{
					return 1;
				}
		}
	}

	private static ArrayList<Rect>	listRects	= new ArrayList<BinearySearch.Rect>();
	private final static int		X_Max		= 10;									// 10行
	private final static int		Y_Max		= 20;									// 10列
	private final static int		rect_width	= 10;									// 模拟方块的宽度
	private final static int		rect_height	= 15;									// 模拟方块的高度
	private final static int		wordPadding	= 2;									// 字间距
	private final static int		linePadding	= 3;									// 行间距

	public static void main(String args[])
	{
		BinearySearch bSearch = new BinearySearch();
		bSearch.init();
		System.out.println("==========size:" + listRects.size());
		bSearch.printRectList();
		Point point = bSearch.new Point();
		point.x = 50;
		point.y = 90;
		int matchIndex = BinarySearchRect(listRects, 0, listRects.size(), point);
		System.out.println("============index:" + matchIndex);
	}

	@SuppressWarnings("unchecked")
	private void printRectList()
	{
		Collections.sort(listRects, new ComparatorRects());
		Iterator<Rect> iterator = listRects.iterator();
		int count = 0;
		while (iterator.hasNext())
		{
			Rect rect = iterator.next();
			System.out.println("====" + count + "=====x1:" + rect.startx
					+ " x2:" + rect.endx + " y1:" + rect.starty + " y2:"
					+ rect.endy);
			count++;
		}
	}

	private void init()
	{
		for (int i = 0; i < X_Max; i++)
		{
			for (int j = 0; j < Y_Max; j++)
			{
				if (j == 0) // 如果是第一行
				{
					Rect rect = new Rect();
					rect.startx = i * (rect_width + wordPadding);
					rect.endx = (i + 1) * (rect_width + wordPadding)
							- wordPadding;
					rect.starty = linePadding;
					rect.endy = rect_height + linePadding;
					listRects.add(rect);
				}
				else
				{
					Rect rect = new Rect();
					rect.startx = i * (rect_width + wordPadding);
					rect.endx = (i + 1) * (rect_width + wordPadding)-wordPadding;
					
					rect.starty = j * (rect_height + linePadding);
					rect.endy = (j + 1) * rect_height + j * linePadding;
					listRects.add(rect);
				}
			}
		}
	}

	/**
	 * 改进用来搜索坐标所在的方块的文字位置
	 * 
	 * @param listRects
	 * @param low
	 * @param high
	 * @param point
	 * @return
	 */
	static int BinarySearchRect(ArrayList<Rect> listRects, int low, int high,
			Point point)
	{
		int mid;
		if (high <= low)
			return -1;
		mid = (low + high) >>> 1; // Or mid = low + ((high - low) / 2)
		if (listRects.get(mid).starty > point.y)
		{

			return BinarySearchRect(listRects, low, mid, point);
		}
		else
			if (listRects.get(mid).endy < point.y)
			{
				return BinarySearchRect(listRects, mid + 1, high, point);
			}
			else
			{
				// 满足的某一行
				if (listRects.get(mid).startx > point.x)
				{
					return BinarySearchRect(listRects, low, mid, point);
				}
				else
					if (listRects.get(mid).endx < point.x)
					{
						return BinarySearchRect(listRects, mid + 1, high, point);
					}
					else
					{
						return mid;
					}
			}
	}
}

打印结果:

==========size:200
====0=====x1:0 x2:10 y1:3 y2:18
====1=====x1:12 x2:22 y1:3 y2:18
====2=====x1:24 x2:34 y1:3 y2:18
====3=====x1:36 x2:46 y1:3 y2:18
====4=====x1:48 x2:58 y1:3 y2:18
====5=====x1:60 x2:70 y1:3 y2:18
====6=====x1:72 x2:82 y1:3 y2:18
====7=====x1:84 x2:94 y1:3 y2:18
====8=====x1:96 x2:106 y1:3 y2:18
====9=====x1:108 x2:118 y1:3 y2:18
====10=====x1:0 x2:10 y1:18 y2:33
====11=====x1:12 x2:22 y1:18 y2:33
====12=====x1:24 x2:34 y1:18 y2:33
====13=====x1:36 x2:46 y1:18 y2:33
====14=====x1:48 x2:58 y1:18 y2:33
====15=====x1:60 x2:70 y1:18 y2:33
====16=====x1:72 x2:82 y1:18 y2:33
====17=====x1:84 x2:94 y1:18 y2:33
====18=====x1:96 x2:106 y1:18 y2:33
====19=====x1:108 x2:118 y1:18 y2:33
====20=====x1:0 x2:10 y1:36 y2:51
====21=====x1:12 x2:22 y1:36 y2:51
====22=====x1:24 x2:34 y1:36 y2:51
====23=====x1:36 x2:46 y1:36 y2:51
====24=====x1:48 x2:58 y1:36 y2:51
====25=====x1:60 x2:70 y1:36 y2:51
====26=====x1:72 x2:82 y1:36 y2:51
====27=====x1:84 x2:94 y1:36 y2:51
====28=====x1:96 x2:106 y1:36 y2:51
====29=====x1:108 x2:118 y1:36 y2:51
====30=====x1:0 x2:10 y1:54 y2:69
====31=====x1:12 x2:22 y1:54 y2:69
====32=====x1:24 x2:34 y1:54 y2:69
====33=====x1:36 x2:46 y1:54 y2:69
====34=====x1:48 x2:58 y1:54 y2:69
====35=====x1:60 x2:70 y1:54 y2:69
====36=====x1:72 x2:82 y1:54 y2:69
====37=====x1:84 x2:94 y1:54 y2:69
====38=====x1:96 x2:106 y1:54 y2:69
====39=====x1:108 x2:118 y1:54 y2:69
====40=====x1:0 x2:10 y1:72 y2:87
====41=====x1:12 x2:22 y1:72 y2:87
====42=====x1:24 x2:34 y1:72 y2:87
====43=====x1:36 x2:46 y1:72 y2:87
====44=====x1:48 x2:58 y1:72 y2:87
====45=====x1:60 x2:70 y1:72 y2:87
====46=====x1:72 x2:82 y1:72 y2:87
====47=====x1:84 x2:94 y1:72 y2:87
====48=====x1:96 x2:106 y1:72 y2:87
====49=====x1:108 x2:118 y1:72 y2:87
====50=====x1:0 x2:10 y1:90 y2:105
====51=====x1:12 x2:22 y1:90 y2:105
====52=====x1:24 x2:34 y1:90 y2:105
====53=====x1:36 x2:46 y1:90 y2:105
====54=====x1:48 x2:58 y1:90 y2:105
====55=====x1:60 x2:70 y1:90 y2:105
====56=====x1:72 x2:82 y1:90 y2:105
====57=====x1:84 x2:94 y1:90 y2:105
====58=====x1:96 x2:106 y1:90 y2:105
====59=====x1:108 x2:118 y1:90 y2:105
====60=====x1:0 x2:10 y1:108 y2:123
====61=====x1:12 x2:22 y1:108 y2:123
====62=====x1:24 x2:34 y1:108 y2:123
====63=====x1:36 x2:46 y1:108 y2:123
====64=====x1:48 x2:58 y1:108 y2:123
====65=====x1:60 x2:70 y1:108 y2:123
====66=====x1:72 x2:82 y1:108 y2:123
====67=====x1:84 x2:94 y1:108 y2:123
====68=====x1:96 x2:106 y1:108 y2:123
====69=====x1:108 x2:118 y1:108 y2:123
====70=====x1:0 x2:10 y1:126 y2:141
====71=====x1:12 x2:22 y1:126 y2:141
====72=====x1:24 x2:34 y1:126 y2:141
====73=====x1:36 x2:46 y1:126 y2:141
====74=====x1:48 x2:58 y1:126 y2:141
====75=====x1:60 x2:70 y1:126 y2:141
====76=====x1:72 x2:82 y1:126 y2:141
====77=====x1:84 x2:94 y1:126 y2:141
====78=====x1:96 x2:106 y1:126 y2:141
====79=====x1:108 x2:118 y1:126 y2:141
====80=====x1:0 x2:10 y1:144 y2:159
====81=====x1:12 x2:22 y1:144 y2:159
====82=====x1:24 x2:34 y1:144 y2:159
====83=====x1:36 x2:46 y1:144 y2:159
====84=====x1:48 x2:58 y1:144 y2:159
====85=====x1:60 x2:70 y1:144 y2:159
====86=====x1:72 x2:82 y1:144 y2:159
====87=====x1:84 x2:94 y1:144 y2:159
====88=====x1:96 x2:106 y1:144 y2:159
====89=====x1:108 x2:118 y1:144 y2:159
====90=====x1:0 x2:10 y1:162 y2:177
====91=====x1:12 x2:22 y1:162 y2:177
====92=====x1:24 x2:34 y1:162 y2:177
====93=====x1:36 x2:46 y1:162 y2:177
====94=====x1:48 x2:58 y1:162 y2:177
====95=====x1:60 x2:70 y1:162 y2:177
====96=====x1:72 x2:82 y1:162 y2:177
====97=====x1:84 x2:94 y1:162 y2:177
====98=====x1:96 x2:106 y1:162 y2:177
====99=====x1:108 x2:118 y1:162 y2:177
====100=====x1:0 x2:10 y1:180 y2:195
====101=====x1:12 x2:22 y1:180 y2:195
====102=====x1:24 x2:34 y1:180 y2:195
====103=====x1:36 x2:46 y1:180 y2:195
====104=====x1:48 x2:58 y1:180 y2:195
====105=====x1:60 x2:70 y1:180 y2:195
====106=====x1:72 x2:82 y1:180 y2:195
====107=====x1:84 x2:94 y1:180 y2:195
====108=====x1:96 x2:106 y1:180 y2:195
====109=====x1:108 x2:118 y1:180 y2:195
====110=====x1:0 x2:10 y1:198 y2:213
====111=====x1:12 x2:22 y1:198 y2:213
====112=====x1:24 x2:34 y1:198 y2:213
====113=====x1:36 x2:46 y1:198 y2:213
====114=====x1:48 x2:58 y1:198 y2:213
====115=====x1:60 x2:70 y1:198 y2:213
====116=====x1:72 x2:82 y1:198 y2:213
====117=====x1:84 x2:94 y1:198 y2:213
====118=====x1:96 x2:106 y1:198 y2:213
====119=====x1:108 x2:118 y1:198 y2:213
====120=====x1:0 x2:10 y1:216 y2:231
====121=====x1:12 x2:22 y1:216 y2:231
====122=====x1:24 x2:34 y1:216 y2:231
====123=====x1:36 x2:46 y1:216 y2:231
====124=====x1:48 x2:58 y1:216 y2:231
====125=====x1:60 x2:70 y1:216 y2:231
====126=====x1:72 x2:82 y1:216 y2:231
====127=====x1:84 x2:94 y1:216 y2:231
====128=====x1:96 x2:106 y1:216 y2:231
====129=====x1:108 x2:118 y1:216 y2:231
====130=====x1:0 x2:10 y1:234 y2:249
====131=====x1:12 x2:22 y1:234 y2:249
====132=====x1:24 x2:34 y1:234 y2:249
====133=====x1:36 x2:46 y1:234 y2:249
====134=====x1:48 x2:58 y1:234 y2:249
====135=====x1:60 x2:70 y1:234 y2:249
====136=====x1:72 x2:82 y1:234 y2:249
====137=====x1:84 x2:94 y1:234 y2:249
====138=====x1:96 x2:106 y1:234 y2:249
====139=====x1:108 x2:118 y1:234 y2:249
====140=====x1:0 x2:10 y1:252 y2:267
====141=====x1:12 x2:22 y1:252 y2:267
====142=====x1:24 x2:34 y1:252 y2:267
====143=====x1:36 x2:46 y1:252 y2:267
====144=====x1:48 x2:58 y1:252 y2:267
====145=====x1:60 x2:70 y1:252 y2:267
====146=====x1:72 x2:82 y1:252 y2:267
====147=====x1:84 x2:94 y1:252 y2:267
====148=====x1:96 x2:106 y1:252 y2:267
====149=====x1:108 x2:118 y1:252 y2:267
====150=====x1:0 x2:10 y1:270 y2:285
====151=====x1:12 x2:22 y1:270 y2:285
====152=====x1:24 x2:34 y1:270 y2:285
====153=====x1:36 x2:46 y1:270 y2:285
====154=====x1:48 x2:58 y1:270 y2:285
====155=====x1:60 x2:70 y1:270 y2:285
====156=====x1:72 x2:82 y1:270 y2:285
====157=====x1:84 x2:94 y1:270 y2:285
====158=====x1:96 x2:106 y1:270 y2:285
====159=====x1:108 x2:118 y1:270 y2:285
====160=====x1:0 x2:10 y1:288 y2:303
====161=====x1:12 x2:22 y1:288 y2:303
====162=====x1:24 x2:34 y1:288 y2:303
====163=====x1:36 x2:46 y1:288 y2:303
====164=====x1:48 x2:58 y1:288 y2:303
====165=====x1:60 x2:70 y1:288 y2:303
====166=====x1:72 x2:82 y1:288 y2:303
====167=====x1:84 x2:94 y1:288 y2:303
====168=====x1:96 x2:106 y1:288 y2:303
====169=====x1:108 x2:118 y1:288 y2:303
====170=====x1:0 x2:10 y1:306 y2:321
====171=====x1:12 x2:22 y1:306 y2:321
====172=====x1:24 x2:34 y1:306 y2:321
====173=====x1:36 x2:46 y1:306 y2:321
====174=====x1:48 x2:58 y1:306 y2:321
====175=====x1:60 x2:70 y1:306 y2:321
====176=====x1:72 x2:82 y1:306 y2:321
====177=====x1:84 x2:94 y1:306 y2:321
====178=====x1:96 x2:106 y1:306 y2:321
====179=====x1:108 x2:118 y1:306 y2:321
====180=====x1:0 x2:10 y1:324 y2:339
====181=====x1:12 x2:22 y1:324 y2:339
====182=====x1:24 x2:34 y1:324 y2:339
====183=====x1:36 x2:46 y1:324 y2:339
====184=====x1:48 x2:58 y1:324 y2:339
====185=====x1:60 x2:70 y1:324 y2:339
====186=====x1:72 x2:82 y1:324 y2:339
====187=====x1:84 x2:94 y1:324 y2:339
====188=====x1:96 x2:106 y1:324 y2:339
====189=====x1:108 x2:118 y1:324 y2:339
====190=====x1:0 x2:10 y1:342 y2:357
====191=====x1:12 x2:22 y1:342 y2:357
====192=====x1:24 x2:34 y1:342 y2:357
====193=====x1:36 x2:46 y1:342 y2:357
====194=====x1:48 x2:58 y1:342 y2:357
====195=====x1:60 x2:70 y1:342 y2:357
====196=====x1:72 x2:82 y1:342 y2:357
====197=====x1:84 x2:94 y1:342 y2:357
====198=====x1:96 x2:106 y1:342 y2:357
====199=====x1:108 x2:118 y1:342 y2:357
============index:54

结论:
坐标:(50,90)刚好在

====54=====x1:48 x2:58 y1:90 y2:105

里,比从头遍历要好很多.