[LeetCode] Merge 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].

/**
 * Definition for an interval.
 * struct Interval {
 *     int start;
 *     int end;
 *     Interval() : start(0), end(0) {}
 *     Interval(int s, int e) : start(s), end(e) {}
 * };
 */

bool comp(const Interval &lhs, const Interval &rhs)
{
    return lhs.start < rhs.start;
}

class Solution {
private:
    vector<Interval> ret;
public:
    vector<Interval> merge(vector<Interval> &intervals) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        ret.clear();
        
        sort(intervals.begin(), intervals.end(), comp);
        for(int i = 0; i < intervals.size(); i++)
            if (ret.size() == 0)
                ret.push_back(intervals[i]);
            else
            {
                int size = ret.size();
                if (ret[size-1].start <= intervals[i].start && intervals[i].start <= ret[size-1].end)
                    ret[size-1].end = max(ret[size-1].end, intervals[i].end);
                else
                    ret.push_back(intervals[i]);
            }
            
            
        return ret;
    }
};