Java - 基于 X 和 Y 坐标对一组点进行排序
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Java - Sorting a Set of Points Based on Both X and Y Coordinates
提问by Shapada
I have a list of point objects that need to be sorted by both X and Y coordinates, but when I pass them to a comparator object only one coordinate gets sorted (the first one called). Any ideas to why this might be happening?
我有一个需要按 X 和 Y 坐标排序的点对象列表，但是当我将它们传递给比较器对象时，只有一个坐标被排序（第一个被调用）。为什么会发生这种情况的任何想法？
static public List<Point> convertToThreeByThreeGrid(String points) {
String[] ptsArray;
List<Point> ptsList = new ArrayList<>();
String stripString = points.replace("[", "").replace("]", "").replace("(", "").replace(")", "").replace(" ", ",").trim();
ptsArray = stripString.split(",");
for(int i = 0; i < ptsArray.length; i += 2) {
int x = Integer.parseInt(ptsArray[i]);
int y = Integer.parseInt(ptsArray[i + 1]);
System.out.println("X: " + x);
System.out.println("Y: " + y);
ptsList.add(new Point(x, y));
}
Collections.sort(ptsList, new Comparator<Point>() {
public int compare(Point a, Point b) {
int result = Integer.compare((int) a.getX(), (int) b.getX());
if (result == 0 ) {
result = Integer.compare((int) a.getY(), (int) b.getY());
}
return result;
}
});
// subtract each coordinate by smallest x and y coordinate values
List<Point> convertedPtList = new ArrayList<>();
int smallestX = (int) ptsList.get(0).getX();
int smallestY = (int) ptsList.get(0).getY();
for (int i = 1; i < ptsList.size(); i++) {
int x = ((int) ptsList.get(i).getX() - smallestX);
int y = ((int) ptsList.get(i).getY() - smallestY);
convertedPtList.add(new Point(x, y));
}
return convertedPtList;
}
}
Output:
输出：
[java.awt.Point[x=10,y=26], java.awt.Point[x=10,y=26], java.awt.Point[x=10,y=28], java.awt.Point[x=12,y=26]]
[java.awt.Point[x=10,y=26], java.awt.Point[x=10,y=26], java.awt.Point[x=10,y=28], java.awt.点[x=12,y=26]]
[java.awt.Point[x=13,y=26], java.awt.Point[x=13,y=28], java.awt.Point[x=13,y=28], java.awt.Point[x=14,y=27], java.awt.Point[x=14,y=27], java.awt.Point[x=15,y=26], java.awt.Point[x=15,y=28], java.awt.Point[x=15,y=28]]
[java.awt.Point[x=13,y=26], java.awt.Point[x=13,y=28], java.awt.Point[x=13,y=28], java.awt.点[x=14,y=27], java.awt.Point[x=14,y=27], java.awt.Point[x=15,y=26], java.awt.Point[x=15] ,y=28], java.awt.Point[x=15,y=28]]
[java.awt.Point[x=16,y=26], java.awt.Point[x=16,y=28], java.awt.Point[x=16,y=28], java.awt.Point[x=18,y=26], java.awt.Point[x=18,y=26], java.awt.Point[x=18,y=28]]
[java.awt.Point[x=16,y=26], java.awt.Point[x=16,y=28], java.awt.Point[x=16,y=28], java.awt.点[x=18,y=26], java.awt.Point[x=18,y=26], java.awt.Point[x=18,y=28]]
回答by JimmyB
for(int i = 0; i < ptsArray.length; i += 2) {
int x = Integer.parseInt(ptsArray[i]);
int y = Integer.parseInt(ptsArray[i+1]);
ptsList.add(new Point(x, y));
}
Collections.sort( ptsList, new Comparator<Point>() {
public int compare(Point x1, Point x2) {
int result = Double.compare(x1.getX(), x2.getX());
if ( result == 0 ) {
// both X are equal -> compare Y too
result = Double.compare(x1.getY(), x2.getY());
}
return result;
}
});
// ptsList is now sorted by both X and Y!
Edit:
编辑：
To just find the lowest X and the lowest Y you can also go the 'classic' way without any (double-)sorting:
要找到最低的 X 和最低的 Y，您也可以采用“经典”方式而无需任何（双）排序：
int minX = Integer.MAX_VALUE;
int minY = Integer.MAX_VALUE;
for ( Point p : ptsList ) {
final int x = (int)p.getX();
final int y = (int)p.getY();
if ( x < minX ) {
minX = x;
}
if ( y < minY ) {
minY = y;
}
}
