Merge Overlapping Intervals

Given a collection of intervals, merge all overlapping intervals.

For example:

Given [1,3],[2,6],[8,10],[15,18],

return [1,6],[8,10],[15,18].

Make sure the returned intervals are sorted.

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/**
 * Definition for an interval.
 * struct Interval {
 *     int start;
 *     int end;
 *     Interval() : start(0), end(0) {}
 *     Interval(int s, int e) : start(s), end(e) {}
 * };
 */
 
 int comp(Interval a , Interval b){
     return a.start<b.start;
 }
 
vector<Interval> Solution::merge(vector<Interval> &A) {
    vector<Interval> res;
    if(A.size() == 0) return res;
    sort(A.begin(),A.end(),comp);
    res.push_back(A[0]);
    for(int i=1 ; i<A.size() ; i++){
        if(res.back().end >= A[i].start){
            res.back().end = max(res.back().end,A[i].end);
        }
        else{
            res.push_back(A[i]);
        }
    }
    return res;
}