合并间隔

来源：互联网发布：微信淘宝优惠卷公众号编辑：程序博客网时间：2024/06/12 00:49

问题：

给一组间隔，把这些间隔合并，使得间隔之间不会有重合。比如：[1, 5], [3, 8], [10, 20], [7, 9] 合并后变成 [1, 9], [10, 20]。

分析：

首先，因为我们需要判断是否两个间隔是否重合，这样才能合并，检查两个间隔是否重合的代码是：

/* * s1: start point of interval 1 * e1: end point of interval 1 * s2: start point of interval 2 * e2: end point of interval 2 */public boolean overlap(int s1, int e1, int s2, int e2) {return Math.max(s1, s2) < Math.min(e1, e2);}

然后，我们把间隔按照开始值排序，这样，从头开始检查，如果当前间隔和前一个间隔重合，就合并。否则，直接把它加入到list里面。

代码如下：

public class Test {//check whether the two intervals intersectpublic boolean overlap(Interval i1, Interval i2) {return Math.max(i1.start, i2.start) < Math.min(i1.end, i2.end);}//merge the intervals and return a new interval list without overlappingpublic void merge(ArrayList<Interval> list) {int currentPosition = 0;for (int i = 1; i < list.size(); i++) {//no intersectionif (overlap(list.get(i), list.get(currentPosition)) == false) {currentPosition++;} else {//get the new intervalint start = Math.min(list.get(i).start, list.get(currentPosition).start);int end = Math.max(list.get(i).end, list.get(currentPosition).end);Interval interval = new Interval(start, end);list.remove(currentPosition);list.add(currentPosition, interval);}}int size = list.size();for (int i = currentPosition + 1; i < size; i++) {list.remove(currentPosition + 1);}}public static void main(String[] args) {ArrayList<Interval> list = new ArrayList<Interval>();list.add(new Interval(3, 8));list.add(new Interval(2, 29));list.add(new Interval(5, 17));list.add(new Interval(22, 47));list.add(new Interval(32, 48));Collections.sort(list);new Test().merge(list);for(Interval inter : list) {System.out.println("[" + inter.start + ", " + inter.end + "]");}}}class Interval implements Comparable<Interval>{int start;int end;Interval(int start, int end) {this.start = start;this.end = end;}public int compareTo(Interval o) {if (start > ((Interval)o).start || (start == ((Interval)o).start && end > ((Interval)o).end)) {return 1;} else if (start == ((Interval)o).start && end == ((Interval)o).end) {return 0;}return -1;}}

转载请注明出处：http://blog.csdn.net/beiyeqingteng