leetcode 56. Merge Intervals

問題

https://leetcode.com/problems/merge-intervals/

解法

首先按照start 排序， 逐個插入，如果與最後一個相交則合併，否則插入新節點。

/**
 * 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> merge(vector<Interval>& intervals) {
        vector<Interval> ret;
        if (intervals.size() ==0)
            return ret;

        sort(intervals.begin(), intervals.end(), 
                [] (const Interval& a, const Interval& b )
                {return a.start < b.start;});
        ret.push_back(intervals[0]);
        for (int i=1; i< intervals.size(); ++i)
        {
            int j= ret.size()-1;
            if (intervals[i].start > ret[j].end)
            {
                ret.push_back(intervals[i]);
            }else{
                ret[j].end = max(ret[j].end, intervals[i].end);
            }
        }
        return ret;
    }
};