56. 合并区间

class Solution {
    public int[][] merge(int[][] intervals) {
        if(intervals.length == 0)
            return new int[][]{};
        //(排序)
         Arrays.sort(intervals, new Comparator<int[]>(){
            @Override
            public int compare(int[] a,int[] b){
                return a[0]-b[0];
            }
        });
        
        List<int[]> res = new ArrayList<>();
        res.add(intervals[0]);
        int i = 0, index = 0;
        while(i < intervals.length) {
            if(res.get(index)[1] >= intervals[i][0]) {
                if(res.get(index)[1] < intervals[i][1])
                    res.get(index)[1] = intervals[i][1];
            } else {
                res.add(intervals[i]);
                index++;
            }
            i++;
        }
        int[][] ans = new int[res.size()][2];
        for(i = 0; i < res.size(); i++) {
            ans[i][0] = res.get(i)[0];
            ans[i][1] = res.get(i)[1];
            
        }
        return ans;
    }
}