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:

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].

Solution:

/**
 * 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 n = intervals.size();
        auto it = intervals.begin();
        while ( it != intervals.end() ) {
            int s = it->start, e = it->end;
            if ( newInterval.end < s or e < newInterval.start ) {it++; continue;}
            newInterval.start = min(s, newInterval.start);
            newInterval.end = max(e, newInterval.end);
            it = intervals.erase(it);
        }
        it = intervals.begin();
        while ( true ) {
            if ( it == intervals.end() or newInterval.start < it->start ) {
                intervals.insert(it, newInterval); 
                return intervals;
            }
            it += 1;
        }
        return intervals;
    }
};

Notes

• Two intervals can not be merged when (1s > 2e) or ( 2s > 1e ); otherwise they can be merged as [min(1s, 2s), max(1e, 2e)].
• When the inserted interval can be merged with intervals[i], we update the inserted interval and delete intervals[i].

/**
 * Definition for an interval.
 * struct Interval {
 *     int start;
 *     int end;
 *     Interval() : start(0), end(0) {}
 *     Interval(int s, int e) : start(s), end(e) {}
 * };
 */
bool compare(Interval a, Interval b ) {
        return ( a.start < b.start );
    }
class Solution {
public:
    vector<Interval> insert(vector<Interval>& intervals, Interval newInterval) {
        auto it = intervals.begin();
        while ( it != intervals.end() ) {
            if ( newInterval.end < it->start or newInterval.start > it->end ) {
                it++; 
                continue;
            }
            newInterval.start = min(newInterval.start, it->start);
            newInterval.end = max(newInterval.end, it->end);
            intervals.erase(it);
        }
        intervals.push_back(newInterval);
        sort(intervals.begin(), intervals.end(), compare);
        return intervals;
    }
};