合并区间

https://leetcode.cn/problems/merge-intervals/description/?envType=study-plan-v2&envId=top-interview-150

这题思维量一般但比较考察API的使用。

1、数组的自定义排序
2、数组的初始化定义
3、Arrays转int
通过重写Comparator的compare方法来自定义排序规则，返回的值看正负。

 Arrays.sort(intervals,new Comparator<int[]>(){
    public int compare(int[] a,int[] b){
        return a[0]-b[0];
    }
});

class Solution {
    public int[][] merge(int[][] intervals) {
        Arrays.sort(intervals,new Comparator<int[]>(){
            public int compare(int[] a,int[] b){
                return a[0]-b[0];
            }
        });
        List<int[]> merge = new ArrayList<>();
        merge.add(intervals[0]);
        for(int i=1;i<intervals.length;i++){
            int left = intervals[i][0];
            int right = intervals[i][1];
            int merge_left = merge.get(merge.size()-1)[0];
            int merge_right = merge.get(merge.size()-1)[1];
            if(left>=merge_left&&left<=merge_right){
                int[] temp = {merge_left,Math.max(right,merge_right)};
                merge.set(merge.size()-1,temp);
            }else{
                merge.add(intervals[i]);
            }
        } 
        //再转化成数组
        return merge.toArray(new int[merge.size()][]);
    }
}