LintCode 合并区间

题目

给出若干闭合区间，合并所有重叠的部分。

样例
给出的区间列表 => 合并后的区间列表：

merge.PNG

代码

/**
 * Definition of Interval:
 * public class Interval {
 *     int start, end;
 *     Interval(int start, int end) {
 *         this.start = start;
 *         this.end = end;
 *     }
 */

class Solution {
    /**
     * @param intervals, a collection of intervals
     * @return: A new sorted interval list.
     */
    public List merge(List intervals) {
        // write your code here
        if (intervals == null || intervals.size() <= 1) {
            return intervals;
        }
        
        Collections.sort(intervals, new IntervalComparator());       
  
        ArrayList result = new ArrayList();
        Interval last = intervals.get(0);
        for (int i = 1; i < intervals.size(); i++) {
            Interval curt = intervals.get(i);
            if (curt.start <= last.end ){
                last.end = Math.max(last.end, curt.end);
            }else{
                result.add(last);
                last = curt;
            }
        }
        
        result.add(last);
        return result;
    }
    
    private class IntervalComparator implements Comparator {
        public int compare(Interval a, Interval b) {
            return a.start - b.start;
        }
    }
}