leetcode 56. Merge Intervals

class Solution {public:vector<Interval> merge(vector<Interval>& intervals) {if (intervals.empty()){return{};}sort(intervals.begin(), intervals.end(), [](const Interval a, const Interval b) {return a.start < b.start; });vector<Interval> res;int index = 0;res.push_back(intervals[0]);for (int i = 1; i < intervals.size(); i++){if (res[index].end < intervals[i].start){index++;res.push_back(intervals[i]);}else{res[index].end = max(res[index].end,intervals[i].end);}}return res;}};