【Java】力扣_每日一题_56. 合并区间_中等

题目链接：https://leetcode-cn.com/problems/merge-intervals/

题目描述
给出一个区间的集合，请合并所有重叠的区间。

第一次编辑代码：（冒泡排序）

class Solution {
    public int[][] merge(int[][] intervals) {
        int n = intervals.length;
        if(n <= 1)
            return intervals;

        for(int i = 0; i < n; i++)
            for(int j = 0; j < n-1; j++){
                if(intervals[j][0] > intervals[j+1][0]){
                    int[] temp = new int[] {intervals[j][0], intervals[j][1]};

                    intervals[j][0] = intervals[j+1][0];
                    intervals[j][1] = intervals[j+1][1];

                    intervals[j+1][0] = temp[0];
                    intervals[j+1][1] = temp[1];
                }
            }

        ArrayList<int[]> overlap = new ArrayList<>();
        int index = 0;
        for(int i = 0; i < n; i++){
            if(overlap.isEmpty()){
                overlap.add(new int[] {intervals[i][0], intervals[i][1]});
            }else{
                if(intervals[i][0] <= overlap.get(index)[1]){
                    if(intervals[i][1] > overlap.get(index)[1])
                        overlap.get(index)[1] = intervals[i][1];
                }else{
                    overlap.add(new int[] {intervals[i][0], intervals[i][1]});
                    index++;
                }
            }
        }

        int[][] ans = new int[overlap.size()][2];
        index = 0;
        for(int[] cur : overlap){
            ans[index][0] = cur[0];
            ans[index][1] = cur[1];
            index++;
        }

        return ans;
    }
}

第二次编辑代码：（比较器排序）

class Solution {
    public int[][] merge(int[][] intervals) {

        if(intervals == null || intervals.length <= 1)
            return intervals;
        
        List<int[]> list = new ArrayList<>();

        Arrays.sort(intervals,new Comparator<int[]>(){
            @Override
            public int compare(int[] o1, int[] o2){
                return o1[0] - o2[0];
            }
        });

        int index = 0;
        int n = intervals.length;
        while(index < n){
            int left = intervals[index][0], right = intervals[index][1];
            while(index < n-1 && right >= intervals[index+1][0]){
                right = Math.max(right, intervals[index+1][1]);
                index++;
            }
            list.add(new int[] {left, right});
            index++;
        }

        return list.toArray(new int[list.size()][2]);
    }
}