[leetcode] Insert Interval

from : https://leetcode.com/problems/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:
    vector<Interval> insert(vector<Interval>& intervals, Interval newInterval) {
        insertCore(intervals, newInterval);
        return mergeCore(intervals);
    }

	void insertCore(vector<Interval>& intervals, Interval newInterval) {
		vector<Interval>::iterator i = intervals.begin(), end = intervals.end();
		int st = newInterval.start;
		while(i != end) {
			if((*i).start >= st) {
				intervals.insert(i, newInterval);
				return;
			}
			++i;
		}
		intervals.emplace_back(newInterval);
	}
    
    vector<Interval> mergeCore(vector<Interval>& intervals) {
        if(1 >= intervals.size()) {
            return intervals;
        }
        vector<Interval> ans;
        int curEd = intervals[0].end, curSt = intervals[0].start;
        for(int i=1, len=intervals.size(); i<len; ++i) {
            if(curEd >= intervals[i].start) {
                if(curEd < intervals[i].end) {
                    curEd = intervals[i].end;
                }
            } else {
                ans.push_back(Interval(curSt, curEd));
                curEd = intervals[i].end;
                curSt = intervals[i].start;
            }
        }
        ans.push_back(Interval(curSt, curEd));
        return ans;
    }
};

下面试超时的代码，思路差不多。

/**
 * 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) {
        insertCore(intervals, newInterval);
        mergeCore(intervals);
        return intervals;
    }

	void insertCore(vector<Interval>& intervals, Interval newInterval) {
		vector<Interval>::iterator i = intervals.begin(), end = intervals.end();
		int st = newInterval.start;
		while(i != end) {
			if((*i).start >= st) {
				intervals.insert(i, newInterval);
				return;
			}
			++i;
		}
		intervals.emplace_back(newInterval);
	}
    
    void mergeCore(vector<Interval>& intervals) {
        if(0 == intervals.size()) {
            return;
        }
        Interval cur = intervals[0];
        for(vector<Interval>::iterator i=++intervals.begin(); i!=intervals.end();) {
            if(cur.end >= (*i).start) {
                cur.end = max(cur.end, (*i).end);
                i = intervals.erase(i);
            } else {
                ++i;
            }
        }
    }
};