【leetcode】Merge Intervals

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

struct cmp
{
bool operator() (Interval a,Interval b)//remember the cmp in sort is not equal in priority_queue
{
if(a.start!=b.start)
return a.start<b.start;
else return a.end<b.end;
}
};

class Solution {
public:
vector<Interval> merge(vector<Interval> &intervals) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
vector<Interval> ans;
if(intervals.empty())
return ans;

sort(intervals.begin(), intervals.end() ,cmp());//cmp()

ans.push_back(intervals[0]);
for(int i=1;i<=intervals.size()-1;i++)
{
int preSta=ans.back().start;
int preEnd=ans.back().end;
int curSta=intervals[i].start;
int curEnd=intervals[i].end;
if(preEnd<curSta)
{
ans.push_back(intervals[i]);
continue;
}
else//should merge
{
ans.back().start=min(preSta,curSta);
ans.back().end=max(preEnd,curEnd);
}
}

return ans;
}
};