08.Merge intervals.java

/*
Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input.

 

Example 1:

Input: intervals = [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Since intervals [1,3] and [2,6] overlap, merge them into [1,6].
Example 2:

Input: intervals = [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [1,4] and [4,5] are considered overlapping.
 

Constraints:

1 <= intervals.length <= 104
intervals[i].length == 2
0 <= starti <= endi <= 104
*/
class Solution {
    public int[][] merge(int[][] intervals) {
        List<int[]>res=new ArrayList<>();
        if(intervals.length==0 || intervals==null)
            return res.toArray(new int[0][]);
        Arrays.sort(intervals,(a,b)->a[0]-b[0]);
        int start=intervals[0][0];
        int end=intervals[0][1];
        for(int[]i:intervals){
            if(i[0]<=end)
                end=Math.max(end,i[1]);
        else{
            res.add(new int[] {start,end});
            start=i[0];
            end=i[1];
        }
    }
    res.add(new int[]{start,end});
    return res.toArray(new int[0][]);
}
}