[LeetCode][Java] Insert Interval

最新推荐文章于 2023-12-19 17:47:54 发布

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最新推荐文章于 2023-12-19 17:47:54 发布

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分类专栏： LeetCode 文章标签： leetcode java Insert Interval

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本文介绍了一种区间合并算法，该算法用于将一个新区间插入到已排序的非重叠区间集合中，并在必要时进行合并。通过两个示例说明了算法的工作原理，包括如何处理新区间的插入以及与其他区间的重叠情况。

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题目：

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

You may assume that the intervals were initially sorted according to their start times.

Example 1:
Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9].

Example 2:
Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and merge [4,9] in as [1,2],[3,10],[12,16].

This is because the new interval [4,9] overlaps with [3,5],[6,7],[8,10].

题意：

给定一组不互相覆盖的间隔数，将一个新的间隔数插入到他们之中（如果必要的话进行合并）.

你可以假设这些间隔数起初是根据他们的起始数排好序的.

样例1：

给定[1,3],[6,9]，插入并合并[2,5] 得到[1,5],[6,9].

样例2：

给定[1,2],[3,5],[6,7],[8,10],[12,16],插入并合并[4,9] 得到 [1,2],[3,10],[12,16].

这是因为新的间隔数[4,9] 覆盖了[3,5],[6,7],[8,10].

算法分析：

* 结合方法《Merge Intervals》
* 新加入 newInterval ,重新排序后然后按照上面的方法就好

AC代码：

<span style="font-size:12px;">public class Solution 
{
    public List<Interval> insert(List<Interval> intervals, Interval newInterval)
    {
    	intervals.add(newInterval);
    	if (intervals == null || intervals.size() <= 1)
            return intervals;
    	return  merge(intervals);
    }  
	public static List<Interval> merge(List<Interval> intervals) 
   {
        if (intervals == null || intervals.size() <= 1)
            return intervals;
        // sort intervals by using self-defined Comparator
        Collections.sort(intervals, new IntervalComparator());
 
        ArrayList<Interval> result = new ArrayList<Interval>();
 
        Interval prev = intervals.get(0);
        for (int i = 1; i < intervals.size(); i++) 
        {
            Interval curr = intervals.get(i);
 
            if (prev.end >= curr.start) 
            {
                // merged case
            Interval merged = new Interval(prev.start, Math.max(prev.end, curr.end));
            prev = merged;
	        } 
	        else 
	        {
	            result.add(prev);
	            prev = curr;
	        }
        }
        result.add(prev);
        return result;
   	}
}
class IntervalComparator implements Comparator<Interval>
{
    public int compare(Interval i1, Interval i2)
    {
        return i1.start - i2.start;
    }
}</span>