ポイントの配列を入力として取り、配列内の各ポイントについて、それ自体以外の最も近いポイントを見つけるメソッドを作成しています。私は現在、力ずくでこれを行っています（すべてのポイントを他のすべてのポイントでチェックしています）。私の現在の実装では配列がソートされていませんが、CompareByX メソッドを使用して px 値でソートできます。アルゴリズムの実行時間をチェックしていますが、n の値が大きいと非常に時間がかかります。私はこのテーマについてあまり知識がなく、さまざまなタイプのデータ構造についてほとんど知りません。簡単な助けがあれば素晴らしいでしょう!
私の現在のコードは次のとおりです。
import java.util.*;
import java.lang.*;
import java.io.*;
class My2dPoint {
double x;
double y;
public My2dPoint(double x1, double y1) {
x=x1;
y=y1;
}
}
class CompareByX implements Comparator<My2dPoint> {
public int compare(My2dPoint p1, My2dPoint p2) {
if (p1.x < p2.x) return -1;
if (p1.x == p2.x) return 0;
return 1;
}
}
/* An object of the above comparator class is used by java.util.Arrays.sort() in main to sort an array of points by x-coordinates */
class Auxiliaries {
public static double distSquared(My2dPoint p1, My2dPoint p2) {
double result;
result = (p1.x-p2.x)*(p1.x-p2.x) + (p1.y-p2.y)*(p1.y-p2.y);
return result;
}
}
public class HW3 {
public static void main (String argv []) throws IOException {
int range = 1000000; // Range of x and y coordinates in points
System.out.println("Enter the number of points");
InputStreamReader reader1 = new InputStreamReader(System.in);
BufferedReader buffer1 = new BufferedReader(reader1);
String npoints = buffer1.readLine();
int numpoints = Integer.parseInt(npoints);
// numpoints is now the number of points we wish to generate
My2dPoint inputpoints [] = new My2dPoint [numpoints];
// array to hold points
int closest [] = new int [numpoints];
// array to record soln; closest[i] is index of point closest to i'th
int px, py;
double dx, dy, dist;
int i,j;
double currbest;
int closestPointIndex;
long tStart, tEnd;
for (i = 0; i < numpoints; i++) {
px = (int) ( range * Math.random());
dx = (double) px;
py = (int) (range * Math.random());
dy = (double) py;
inputpoints[i] = new My2dPoint(dx, dy);
}
// array inputpoints has now been filled
tStart = System.currentTimeMillis();
// find closest [0]
closest[0] = 1;
currbest = Auxiliaries.distSquared(inputpoints[0],inputpoints[1]);
for (j = 2; j < numpoints; j++) {
dist = Auxiliaries.distSquared(inputpoints[0],inputpoints[j]);
if (dist < currbest) {
closest[0] = j;
currbest = dist;
}
}
// now find closest[i] for every other i
for (i = 1; i < numpoints; i++) {
closest[i] = 0;
currbest = Auxiliaries.distSquared(inputpoints[i],inputpoints[0]);
for (j = 1; j < i; j++) {
dist = Auxiliaries.distSquared(inputpoints[i],inputpoints[j]);
if (dist < currbest) {
closest[i] = j;
currbest = dist;
}
}
for (j = i+1; j < numpoints; j++) {
dist = Auxiliaries.distSquared(inputpoints[i],inputpoints[j]);
if (dist < currbest) {
closest[i] = j;
currbest = dist;
}
}
}
tEnd = System.currentTimeMillis();
System.out.println("Time taken in Milliseconds: " + (tEnd - tStart));
}
}