Merge Intervals

Merge Intervals

问题：

Given a collection of intervals, merge all overlapping intervals.

思路：

　　不排序 直接上根据交集的特性

　　排序后再判断

　　简单的数学推导

我的代码1：

public class Solution {

    public List<Interval> merge(List<Interval> intervals) {

        if(intervals == null || intervals.size() == 0)  return intervals;

        for(int i = 0; i < intervals.size(); i++)

        {

            Interval interval = intervals.get(i);

            int min = interval.start;

            int max = interval.end;

            for(int j = i+1; j < intervals.size(); j++)

            {

                Interval tmp = intervals.get(j);

                if(isIntersect(interval, tmp))

                {

                    intervals.remove(j);

                    j--;

                    max = Math.max(max, tmp.end);

                    min = Math.min(min, tmp.start);

                }

            }

            if(min == interval.start && max == interval.end) i++;

            interval.start = min;

            interval.end = max;

            i--;

        }

        return intervals;

    }

    public boolean isIntersect(Interval one, Interval two)

    {

        int oneS = one.start;

        int oneE = one.end;

        int twoS = two.start;

        int twoE = two.end;

        if(oneE >= twoS && oneE <= twoE)    return true;

        if(twoE >= oneS && twoE <= oneE)    return true;

        if(oneE >= twoE && oneS <= twoS)    return true;

        if(twoE >= oneE && twoS <= oneS)    return true;

        return false;

    }

}

View Code

我的代码2：

public class Solution {

    public List<Interval> merge(List<Interval> intervals) {

        if(intervals == null || intervals.size() == 0)  return intervals;

        Collections.sort(intervals, new IntervalComparator());

        for(int i = 0; i < intervals.size() - 1; i++)

        {

            Interval one = intervals.get(i);

            Interval two = intervals.get(i+1);

            if(one.end >= two.start)

            {

                one.end = Math.max(one.end, two.end);

                intervals.remove(i+1);

                i--;

            }

        }

        return intervals;

    }

    private class IntervalComparator implements Comparator<Interval>

    {

        public int compare(Interval a, Interval b)

        {

            return a.start - b.start;

        }

    }

}

View Code