【Leetcode】57. 插入区间

输入: intervals = [[1,3],[6,9]], newInterval = [2,5]
输出: [[1,5],[6,9]]

输入: intervals = [[1,2],[3,5],[6,7],[8,10],[12,16]], newInterval = [4,8]
输出: [[1,2],[3,10],[12,16]]
解释: 这是因为新的区间 [4,8] 与 [3,5],[6,7],[8,10] 重叠。

[1,2],[3,5] (没有重叠)
[1,2],[3,5],[4,8] -> [1,2],[3,8] (有重叠,合并.)
[1,2],[3,8],[6,7] -> [1,2],[3,8] (有重叠,合并.)
[1,2],[3,8],[8,10] -> [1,2],[3,10] (有重叠,合并.)
[1,2],[3,10][12,16] (没有重叠)

/**
 * Definition for an interval.
 * public class Interval {
 *     int start;
 *     int end;
 *     Interval() { start = 0; end = 0; }
 *     Interval(int s, int e) { start = s; end = e; }
 * }
 */
class Solution {
    public List<Interval> insert(List<Interval> intervals, Interval newInterval) {
        intervals.add(newInterval);
        //按照start升序排列,原来的顺序也是能保证的.
        intervals.sort(Comparator.comparingInt(e -> e.start));
        List<Interval> newList = new ArrayList<>();
        newList.add(intervals.get(0));
        for(int i=1; i< intervals.size() ; i++) {
            Interval entry = intervals.get(i);
            Interval last = newList.get(newList.size()-1);
            if (last.start <= entry.start && last.end >= entry.start) {
                //有重叠,合并.
                last.end = Math.max(entry.end,last.end);
            } else {
                //没有重叠
                newList.add(entry);
            }
        }
        return newList;
    }
}