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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) {}
 * };
 */

//方法：先sort，然后再考虑情况合并。复杂度：O(nlogn)
class Solution {
public:
    struct compare {
        bool operator()( const Interval& a , const Interval& b) const {
            if( a.start==b.start)
                return a.end < b.end;
            else
                return a.start < b.start;
        }
    };

	vector<Interval> merge(vector<Interval> &intervals) {
	    if(intervals.size()==0)
	        return vector<Interval>();
	    sort(intervals.begin() , intervals.end() , compare());
	    vector<Interval> ans;
	    Interval temp;
	    temp = intervals[0];
	    for(int i=1; i<intervals.size(); i++)
	    {
	        if(intervals[i].start <= temp.end )
	            temp.end = max(intervals[i].end , temp.end);
	        else
            {
                ans.push_back(temp);
                temp = intervals[i];
            }
	    }
	    ans.push_back(temp);
	    return ans;
	}
};