题解 | #合并区间#

import java.util.*;

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

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param intervals Interval类ArrayList 
     * @return Interval类ArrayList
     */
    public ArrayList<Interval> merge (ArrayList<Interval> intervals) {
        // write code here
        // 按照start进行排序
        Collections.sort(intervals , (int1 ,int2)->int1.start - int2.start);
        // 定义所需变量
        int dest = 0,cur = 0,n = intervals.size(),count = 0;
        // 处理特殊情况：没有数据与只有一个数据
        if (n <= 1) {
            return intervals;
        }
        // 开始循环遍历：  思路：从异地到就地
        for (cur = 1; cur < n; cur++) {
            if (intervals.get(cur).start <= intervals.get(dest).end) {
                intervals.get(dest).start = Math.min(Math.min(intervals.get(dest).start,intervals.get(cur).start),Math.min(intervals.get(dest).end,intervals.get(cur).end));
                intervals.get(dest).end = Math.max(Math.max(intervals.get(dest).end,intervals.get(cur).end),Math.max(intervals.get(dest).start,intervals.get(cur).start));
                count++;
            } else {
                dest++;
                intervals.get(dest).end = intervals.get(cur).end;
                intervals.get(dest).start = intervals.get(cur).start;  
            }
        }
        // 删除无效数据
        for (int i = 0; i < count; i++) {
            intervals.remove(n - 1 - i);
        }
        return intervals;
    }
}