力扣56.合并区间

• 按左端点排序

  • 判断左端点是否小于等于当前右端点**（可以合并）**

•   class Solution {
    public:
        vector<vector<int>> merge(vector<vector<int>>& intervals) {
            ranges::sort(intervals);
            vector<vector<int>> res;
            for(auto &t:intervals)
            {
                if(!res.empty() && t[0] <= res.back()[1])
                    res.back()[1] = max(res.back()[1],t[1]);
                else
                    res.emplace_back(t);
            }
            return res;
        }
    };