[leetcode]Insert Interval

/**
 * 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:
    vector<Interval> insert(vector<Interval> &intervals, Interval newInterval) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<Interval> pre;
        vector<Interval> post;
        
        int low = newInterval.start;
        int high = newInterval.end;
        
        for(int i = 0; i < intervals.size(); i++){
            if(intervals[i].end < low){
                pre.push_back(intervals[i]);
            }
            if(intervals[i].start > high){
                post.push_back(intervals[i]);
            }
        }
        
        int p;
        
        if(intervals.empty() || pre.size() == intervals.size()){
            p = low;
        }else{
            p = min(low, intervals[pre.size()].start);
        }
        
        int q;
        if(intervals.empty() || post.size() == intervals.size()){
            q = high;
        }else{
            q = max(high, intervals[intervals.size()-1-post.size()].end);
        }
        
        pre.push_back(Interval(p,q));
        pre.insert(pre.end(), post.begin(), post.end());
        
        return pre;
        
    }
};