leetcode merge intervals-优快云博客

本文链接：https://blog.youkuaiyun.com/neostar2008/article/details/9462893

本文介绍了一种区间合并算法的实现方式，通过定义一个Interval类来表示区间，并使用自定义比较器进行排序，最后通过遍历合并区间，实现了有效的区间合并功能。

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import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;

class Interval {
	int start;
	int end;
	Interval() {start = 0; end = 0;}
	Interval(int s, int e) {start = s; end = e;}
}

public class MergeInterval {
	/**
	 * 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 MyComparator implements Comparator {

		@Override
		public int compare(Object o1, Object o2) {
			// 
			Interval i1 = (Interval) o1;
			Interval i2 = (Interval) o2;
			if(i1.start < i2.start) return -1;
			if(i1.start > i2.start) return 1;
			if(i1.start == i2.start && i1.end < i2.end) return -1;
			if(i1.start == i2.start && i1.end > i2.end) return 1;
			return 0;
		}
		
	}
	
    public ArrayList<Interval> merge(ArrayList<Interval> intervals) {
    	ArrayList<Interval> result = new ArrayList<Interval>();
    	MyComparator mc = new MyComparator();
    	Collections.sort(intervals, mc);

    	for(Interval cur : intervals) {
    		if(result.isEmpty()) {
    			result.add(cur);
    		} else {
    			Interval last = result.get(result.size() - 1);
    			if(last.end < cur.start) {
    				result.add(cur);
    			} else {
    				last.end = last.end > cur.end ? last.end : cur.end;
    			}
    		}
    	}
        return result;
    }
	

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// 
		ArrayList<Interval> test = new ArrayList<Interval>();
		test.add(new Interval(1,3));
		test.add(new Interval(2,6));
		test.add(new Interval(8,10));
		test.add(new Interval(15,18));
		
		MergeInterval mi = new MergeInterval();
		ArrayList<Interval> res = mi.merge(test);
		for(Interval in : res) {
			System.out.println(in.start + " " + in.end);
		}

	}

}