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 {
    /**
     * 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) {
        // write code here

        int n = intervals.size();
        ArrayList<Interval> ans = new ArrayList<Interval>();
        if(n==0)return intervals;
        Collections.sort(intervals, new Comparator<Interval>(){
            public int compare(Interval o1, Interval o2){
                if(o1.start != o2.start)
                    return o1.start - o2.start;
                else
                    return o1.end - o2.end;
            }
        }); 
        int i=0;
        Interval cur=intervals.get(0);
        while(i<n){
            Interval nxt = intervals.get(i);
            if(nxt.start<=cur.end){
                cur.end=Math.max(cur.end,nxt.end);
            }else{
                ans.add(cur);
                cur=nxt;
            }
            i+=1;
        }
        ans.add(cur);
        return ans;
    }
}