FG面经： Interval问题合集

How to insert interval to an interval list. List is not sorted

O(N) solution:

package fb;
import java.util.*;

class Interval {
    int start;
    int end;
    public Interval(int s, int e) {
        start = s;
        end = e;
    }
}


public class InsertInterval {


    
    public List<Interval> insert(List<Interval> intervals, Interval newInterval) {

        ArrayList<Interval> res = new ArrayList<Interval>();
        for (Interval interval : intervals) {
            if (interval.end < newInterval.start || interval.start>newInterval.end) {
                res.add(interval);
            }
            else {
                newInterval.start = Math.min(newInterval.start, interval.start);
                newInterval.end = Math.max(newInterval.end, interval.end);
            }
        }
        res.add(newInterval);
        return res;
    }
    
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        InsertInterval sol = new InsertInterval();
        Interval i1 = new Interval(1,3);
        Interval i2 = new Interval(6,9);
        Interval i3 = new Interval(100,102);
        List<Interval> intervals = new ArrayList<Interval>();
        intervals.add(i2);
        intervals.add(i1);
        intervals.add(i3);
        List<Interval> res = sol.insert(intervals, new Interval(3,7));
        for (Interval each : res) {
            System.out.print(each.start);
            System.out.println(each.end);
        }
    }

}

两个interval overlap条件：

interval1.end >= interval2.start && interval1.start <= interval2.end

问：一个query数在不在已经加入的区间？

如果interval是sorted, 就可以binary search, 插入位置的上一个interval, 判断是否在那个interval里面

如果没有sorted, 只能挨个比了