MelkmanバンプアルゴリズムのJava実装
5688 ワード
座標オブジェクト:
アルゴリズムとテスト:
public class Point{
private float x; //X
private float y; //Y
private double arCos; // P0
public float getX() {
return x;
}
public void setX(float x) {
this.x = x;
}
public float getY() {
return y;
}
public void setY(float y) {
this.y = y;
}
public double getArCos() {
return arCos;
}
public void setArCos(double arCos) {
this.arCos = arCos;
}
}
アルゴリズムとテスト:
package Melkman;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
/**
* Melkman
* @author zl
*/
public class Melkman {
private Point[] pointArray;//
private final int N;//
private int D[]; //
public Melkman(List pList) {
this.pointArray = new Point[pList.size()];
N = pList.size();
int k = 0;
for (Point p : pList) {
pointArray[k++] = p;
}
D = new int[2 * N];
}
/**
*
*
* @return
*/
public Point[] getTubaoPoint() {
// Y, P0
float minY = pointArray[0].getY();
int j = 0;
for (int i = 1; i < N; i++) {
if (pointArray[i].getY() < minY) {
minY = pointArray[i].getY();
j = i;
}
}
swap(0, j);
// x
for (int i = 1; i < N; i++) {
pointArray[i].setArCos(angle(i));
}
quickSort(1, N - 1); //
int bot = N - 1;
int top = N;
D[top++] = 0;
D[top++] = 1;
int i;
for (i = 2; i < N; i++) {// 3 !!
if (isLeft(pointArray[D[top - 2]], pointArray[D[top - 1]],
pointArray[i]) != 0)
break;
D[top - 1] = i; //
}
D[bot--] = i;
D[top++] = i; // i !!
int t;
if (isLeft(pointArray[D[N]], pointArray[D[N + 1]], pointArray[D[N + 2]]) < 0) {
// 3 , 3 a,b,c , ab
t = D[N];
D[N] = D[N + 1];
D[N + 1] = t;
}
for (i++; i < N; i++) {
// i , //top=n+3 bot=n-2
if (isLeft(pointArray[D[top - 2]], pointArray[D[top - 1]],
pointArray[i]) > 0
&& isLeft(pointArray[D[bot + 1]], pointArray[D[bot + 2]],
pointArray[i]) > 0) {
continue;
}
//
while (isLeft(pointArray[D[top - 2]], pointArray[D[top - 1]],
pointArray[i]) <= 0) {
top--;
}
D[top++] = i;
//
while (isLeft(pointArray[D[bot + 1]], pointArray[D[bot + 2]],
pointArray[i]) <= 0) {
bot++;
}
D[bot--] = i;
}
// ,D bot+1 top-1 ( )
Point[] resultPoints = new Point[top - bot - 1];
int index = 0;
for (i = bot + 1; i < top - 1; i++) {
System.out.println(pointArray[D[i]].getX() + ","
+ pointArray[D[i]].getY());
resultPoints[index++] = pointArray[D[i]];
}
return resultPoints;
}
/**
* ba ao
*
* @return 0
*/
private float isLeft(Point o, Point a, Point b) {
float aoX = a.getX() - o.getX();
float aoY = a.getY() - o.getY();
float baX = b.getX() - a.getX();
float baY = b.getY() - a.getY();
return aoX * baY - aoY * baX;
}
/**
*
*
* @param i
* @param j
*/
private void swap(int i, int j) {
Point tempPoint = new Point();
tempPoint.setX(pointArray[j].getX());
tempPoint.setY(pointArray[j].getY());
tempPoint.setArCos(pointArray[j].getArCos());
pointArray[j].setX(pointArray[i].getX());
pointArray[j].setY(pointArray[i].getY());
pointArray[j].setArCos(pointArray[i].getArCos());
pointArray[i].setX(tempPoint.getX());
pointArray[i].setY(tempPoint.getY());
pointArray[i].setArCos(tempPoint.getArCos());
}
/**
*
*
* @param top
* @param bot
*/
private void quickSort(int top, int bot) {
int pos;
if (top < bot) {
pos = loc(top, bot);
quickSort(top, pos - 1);
quickSort(pos + 1, bot);
}
}
/**
* , ,
*
* @param top
* @param bot
* @return
*/
private int loc(int top, int bot) {
double x = pointArray[top].getArCos();
int j, k;
j = top + 1;
k = bot;
while (true) {
while (j < bot && pointArray[j].getArCos() < x)
j++;
while (k > top && pointArray[k].getArCos() > x)
k--;
if (j >= k)
break;
swap(j, k);
}
swap(top, k);
return k;
}
/**
*
*
* @param i
* @return
*/
private double angle(int i) {
double j, k, m, h;
j = pointArray[i].getX() - pointArray[0].getX();
k = pointArray[i].getY() - pointArray[0].getY();
m = Math.sqrt(j * j + k * k); // i
if (k < 0)
j = (-1) * Math.abs(j);
h = Math.acos(j / m); // x
return h;
}
public static void main(String args[]) {
// File file = new File("G:/yl.txt");
File file = new File("G:/data.txt");
BufferedReader br = null;
try {
br = new BufferedReader(new FileReader(file));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
List pointList = new ArrayList();
String str = null;
try {
str = br.readLine();
} catch (IOException e) {
e.printStackTrace();
}
while (str != null) {
String[] s = str.split("\\t", 2);
float x = Float.parseFloat(s[0].trim());
float y = Float.parseFloat(s[1].trim());
Point p = new Point();
p.setX(x);
p.setY(y);
// System.out.println(" :" + x + ", " + y);
pointList.add(p);
try {
str = br.readLine();
} catch (IOException e) {
e.printStackTrace();
}
}
System.out.println(" :" + pointList.size());
Melkman m = new Melkman(pointList);
m.getTubaoPoint();
}
}