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int cmp(Interval a, Interval b) {
    if(a.start == b.start)
        return a.end < b.end;
    return a.start < b.start;
}

class Solution {
public:
    vector<Interval> merge(vector<Interval> &intervals) {
        sort(intervals.begin(), intervals.end(), cmp);
        vector<Interval> ans;
        ans.clear();
        if(intervals.size() <= 0) return ans;
        Interval item = intervals[0];
        for(int i = 1; i < intervals.size(); i++) {
            if(item.end < intervals[i].start) {
                ans.push_back(item);
                item = intervals[i];
            }
            else {
                if(item.end < intervals[i].end)
                    item.end = intervals[i].end;
            }
        }
        ans.push_back(item);
        return ans;
    }
};