leetcode Merge Intervals

MergeIntervals.cpp

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