LeetCode 56 合并区间

// LeetCode 56 合并区间
// 二维排序,依次取出区间进行比较,O(nlogn))复杂度


class Solution {

    public int[][] merge(int[][] intervals) {
        int n = intervals.length;
        if (n == 0) return new int[0][0];
        Interval[] interval = new Interval[n];
        for (int i = 0;i < n; i++){
            interval[i] = new Interval(intervals[i][0],intervals[i][1]);
        }
        Arrays.sort(interval);
        // print(interval);

        List<Interval> res = new ArrayList<>();
        Interval ans = interval[0];
        for (int i = 1;i < n;i ++){
            if (ans.second < interval[i].first) {
                res.add(ans);
                ans = interval[i];
            }else {
                ans.second = Math.max(ans.second,interval[i].second);
            }
        }

        res.add(ans);
        
        // printL(res);
        
        int m = res.size();
        int[][] answer = new int[m][2];
        for (int i = 0;i < m;i ++){
            ans = res.get(i);
            answer[i][0] = ans.first;
            answer[i][1] = ans.second;
        }
        return answer;
    }

    class Interval implements Comparable{
        int first;
        int second;

        public Interval() {
            first = 0;
            second = 0;
        }

        public Interval(int a, int b){
            first = a;
            second = b;
        }

        @Override
        public int compareTo(Object o) {
            if (o instanceof Interval) {
                Interval in = (Interval) o;
                if (first < in.first || first == in.first && second < in.second)
                    return -1;
                else if (first == in.first && second == in.second)
                    return 0;
                return 1;
            }
            return 0;
        }

    }

    public void print(Interval[] in){
        for (int i = 0;i < in.length; i++){
            System.out.println(in[i].first + " " + in[i].second);
        }
    }

    public void printL(List<Interval> res) {
        for (Interval o : res){
            System.out.println(o.first + " " + o.second);
        }
    }
}