Insert Interval_2.cpp

/**
 * 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) {
        int len = intervals.size(), lo = 0, hi = len - 1;
        if(intervals.empty() || intervals.back().end < newInterval.start){intervals.push_back(newInterval); return intervals;};
        int head = find(intervals, newInterval.start, 0, len - 1, true), tail = find(intervals, newInterval.end, 0, len, false) - 1;
        vector<Interval> res;
        for(int i = 0; i < head; ++i)res.push_back(intervals[i]);
        Interval mergedInterval(min(intervals[head].start, newInterval.start), max(intervals[tail].end, newInterval.end));
        res.push_back(mergedInterval);
        for(int i = tail + 1; i < len; ++i)res.push_back(intervals[i]);
        return res;
    }

private:
    int find(vector<Interval>& intervals, int target, int lo, int hi, bool isHead)
    {
        while(lo < hi)
        {
            int mid = lo + (hi - lo) / 2;
            int curr = isHead? intervals[mid].end: intervals[mid].start;
            if(isHead)
            {
                if(curr >= target)hi = mid;
                else lo = mid + 1;
            }
            else
            {
                if(curr <= target)lo = mid + 1;
                else hi = mid;
            }
        }
        return lo;
    }
};