Sweep Line & Interval
不需要检测每一时刻，只需要检测起点或者终点的位置！（交点变化的位置只有起点或者终点）
- 1.将数据拆成二元组 [起点/终点标识，时刻]
- 2.按照时刻排序
- 3.依次扫描
...the simple but powerful idea of a sweep line: a vertical line that is conceptually “swept” across the plane. In practice, of course, we cannot simulate all points in time and so we consider only some discrete points.
class Point{
int time;
int flag; // 1=start, 0=end
Point(int time, boolean flag){
this.time = time;
this.flag = flag;
}
public static Comparator<Point> pointComparator = new Comparator<Point>() {
public int compare(Point p1, Point p2){
// 如果时间一致，如果两个都是start或都是end，那么它两相等。如果p1是start而p2是end，那么p1 > p2
if (p1.time == p2.time) return p1.flag - p2.flag;
else return p1.time - p2.time;
}
}
Last modified 2yr ago