【leetcode】Merge Intervals

Merge Intervals

Given a collection of intervals, merge all overlapping intervals.

For example,
Given [1,3],[2,6],[8,10],[15,18],
return [1,6],[8,10],[15,18].

 

 

先排序，然后循环合并

 

/**
 * 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> result;
        if(intervals.empty()) return result;
       
        sort(intervals.begin(),intervals.end(),cmp);
       
        int start=intervals[0].start;
        int end=intervals[0].end;
       
        for(int i=1;i<intervals.size();i++)
        {
            if(intervals[i].start<=end)
            {
                //注意[1,4],[2,3]的情况
                end=end<intervals[i].end?intervals[i].end:end;
            }
            else
            {
                result.push_back(Interval(start,end));
                start=intervals[i].start;
                end=intervals[i].end;
            }
        }
 
        result.push_back(Interval(start,end));
        return result;
    }
   
    static int cmp(const Interval &a,const Interval &b)
    {
        if(a.start<b.start) return 1;
        else if(a.start>b.start) return 0;
        else return a.end<b.end;
    }
};