57. 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:

Input: intervals = [[1,3],[6,9]], newInterval = [2,5]
Output: [[1,5],[6,9]]

Example 2:

Input: intervals = [[1,2],[3,5],[6,7],[8,10],[12,16]], newInterval = [4,8]
Output: [[1,2],[3,10],[12,16]]
Explanation: Because the new interval [4,8] overlaps with [3,5],[6,7],[8,10].

AC code:

/**
 * 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) {
        intervals.push_back(newInterval);
        sort(intervals.begin(), intervals.end(),
             [](Interval& a, Interval& b) {
                 return a.start < b.start;
             });
        vector<Interval> ans;
        for (const auto interval : intervals) {
            if (ans.empty() || ans.back().end  < interval.start) {
                ans.push_back(interval);
            } else {
                ans.back().end = max(ans.back().end, interval.end);
            }
        }
        return ans;
    }
};

Runtime: 12 ms, faster than 50.31% of C++ online submissions for Insert Interval.