Merge Intervals

 1 /**
 2  * Definition for an interval.
 3  * struct Interval {
 4  *     int start;
 5  *     int end;
 6  *     Interval() : start(0), end(0) {}
 7  *     Interval(int s, int e) : start(s), end(e) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     vector<Interval> merge(vector<Interval> &intervals) {
13         vector<Interval> ans;   //存放合并后的区间
14         if( intervals.empty() ) return ans;
15         sort(intervals.begin(), intervals.end(), cmp);  //排序
16         ans.push_back(intervals[0]);    //先设置intervals[0]为当前区间
17         for(int i=1; i<intervals.size(); ++i) {
18             if( intervals[i].start >= ans.back().start && intervals[i].start <= ans.back().end ) {  //一、二、三情况内
19                 if( intervals[i].end > ans.back().end ) ans.back().end = intervals[i].end;
20             }
21             else ans.push_back( intervals[i] ); //第四种情况
22         }
23         return ans;
24     }
25     
26 private:
27     static bool cmp(const Interval& lhs, const Interval& rhs) {
28         if( lhs.start == rhs.start ) return lhs.end < rhs.end;
29         else return lhs.start < rhs.start;
30     }
31 };