leetcode_merge_intervals

/**
 * Definition for an interval.
 * struct Interval {
 *     int start;
 *     int end;
 *     Interval() : start(0), end(0) {}
 *     Interval(int s, int e) : start(s), end(e) {}
 * };
 */
class Solution {
public:
    vector<Interval> merge(vector<Interval>& intervals) {
        vector<Interval> ret;
        if(intervals.empty()) return ret;
        sort(intervals.begin(), intervals.end(),[](Interval &lhs,Interval &rhs){return lhs.start < rhs.start;});	//lambda函数
        auto it = intervals.begin();
        int merge_start = -1, merge_end = -1;
        for(; it != intervals.end(); it++)
        {
            if(merge_start == -1 && merge_end == -1)
            {
                merge_start = it->start;
                merge_end = it->end;
            }
            else
            {
                if(merge_end < it->start)
                {
                    ret.push_back(Interval(merge_start, merge_end));
                    merge_start=it->start;
                    merge_end=it->end;
                }
                else if(merge_end >= it->start)
                {
                    merge_end = max(merge_end, it->end);
                }
            }
        }
        ret.push_back(Interval(merge_start, merge_end));
        return ret;
    }
};