leetcode[56]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) {}
 * };
 */
 /**
采用自定义的比较函数，必须申明为全局对象，不能是类的局部对象。
*/
bool comp(const Interval &a, const 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) 
{    
    vector<Interval> res;
    if(intervals.empty())return res;    
    sort(intervals.begin(),intervals.end(),comp);
    Interval temp(intervals[0].start, intervals[0].end);
    for (int i=1;i<intervals.size();i++)
    {
        if (intervals[i].start<=temp.end)
        {
            temp.end=temp.end>intervals[i].end?temp.end:intervals[i].end;
        } 
        else
        {
            res.push_back(temp);
            temp.start=intervals[i].start;
            temp.end=intervals[i].end;
        }
    }
    res.push_back(temp);
    return res;
}
};