题解 | #合并区间#

import java.util.*;


//  public class Interval {
//     int start;
//     int end;
//     public Interval(int start, int end) {
//         this.start = start;
//         this.end = end;
//   }
// }


public class Solution {
    // public static void main(Args[] args){

    // }
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param intervals Interval类ArrayList
     * @return Interval类ArrayList
     */
    public ArrayList<Interval> merge (ArrayList<Interval> intervals) {
        Collections.sort(intervals, new Comparator<Interval>() {
            @Override
            public int compare(Interval i1, Interval i2) {
                if (i1.start != i2.start)
                    return i1.start - i2.start;
                else
                    return i1.end - i2.end;
            }
        });
        // write code here
        ArrayList<Interval> al = new ArrayList();
        for (int i = 0; i < intervals.size(); i++) {
            Interval outl = new Interval(0, 0);
            Interval il = intervals.get(i);
            if (al.size() == 0) {
                al.add(il);
                continue;
            } else {
                outl = al.get(al.size() - 1);
            }
            if (outl.end >= il.start) { // merge
                al.remove(al.size() - 1);
                al.add(new Interval(outl.start, Math.max(il.end,outl.end)));
                continue;
            }
            al.add(il);
        }
        return al;
    }
}

知识点 ：

复杂对象数组类型排序

Collections.sort(intervals, new Comparator<Interval>() {

@Override

public int compare(Interval i1, Interval i2) {

if (i1.start != i2.start)

return i1.start - i2.start;

else

return i1.end - i2.end;

}

});

注意边界值