[Leetcode]Insert Interval

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

You may assume that the intervals were initially sorted according to their start times.

Example 1:
Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9].

Example 2:
Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and merge [4,9] in as [1,2],[3,10],[12,16].

This is because the new interval [4,9] overlaps with [3,5],[6,7],[8,10].

/**
 * 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:
    /*algorithm
        similar as merge interval
    */
    vector<Interval> insert(vector<Interval>& intervals, Interval newInterval) {
            vector<Interval>ret;
            intervals.push_back(Interval(INT_MAX,INT_MAX));//as end mark
            //first insert
            int i = 0;
            for(;i < intervals.size();++i){
                if(newInterval.start < intervals[i].start ||
                   (newInterval.start == intervals[i].start && 
                   newInterval.end < intervals[i].end)){
                     break;
                   }
            }
            intervals.insert(intervals.begin()+i,newInterval);//insert element
            //second merge
            Interval cur=intervals[0];
            for(int i = 1;i < intervals.size();i++){
                if(cur.end >= intervals[i].start){//overlap
                    cur.start = min(cur.start,intervals[i].start);
                    cur.end = max(cur.end,intervals[i].end);
                }else{
                    ret.push_back(cur);
                    cur = intervals[i];
                }
            }
            return ret;
    }
};