[LeetCode] 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].

在LeetCode“Insert Interval”的基础上写的代码：

/**
 * 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) {
        int len = intervals.size();
        vector<Interval> res;
        for(int i=0;i<len;i++){
          res = insert(res,intervals[i]);
        }
        return res;
    }
private:
    vector<Interval> insert(vector<Interval> &intervals, Interval newInterval) {
        vector<Interval> result;
        Interval temp;
        int len = intervals.size();
        if(len==0){ //特殊情况，intervals是空时直接可以得到结果
            result.push_back(newInterval);
            return result;
        }
            
        int startIndex,endIndex;
        int i,startflag=0,endflag=0;
        for(i = 0;i<len;){
            if(intervals[i].start<=newInterval.start && intervals[i].end >= newInterval.end){//新区间在某个区间内
                return intervals;
            }else if(startflag == 0 && intervals[i].start > newInterval.end ){//新区间在所有区间外，在某个区间之前
                result.push_back(newInterval);
                startflag = 1;
                endflag = 1;
                break;
            }else if(intervals[i].end < newInterval.start && i!=len-1){//新区间的起点在此区间之后
                result.push_back(intervals[i]);
                i++;
            }else if(startflag == 0 && newInterval.start < intervals[i].start && 
                newInterval.end >=  intervals[i].start && newInterval.end <= intervals[i].end){//新区间的起点在此区间之前，终点在此区间之间
                startflag = 1;
                endflag = 1;
                temp.start  = newInterval.start;
                temp.end    = intervals[i].end;
                result.push_back(temp);
                i++;
                break;
            }else if(startflag == 0 && newInterval.start < intervals[i].start &&
                newInterval.end > intervals[i].end){ //新区间的起点在此区间之前，终点超出此区间
                startflag = 1;
                temp.start  = newInterval.start;
                
            }else if(startflag == 0 && newInterval.start >= intervals[i].start &&
                newInterval.start <=  intervals[i].end && newInterval.end > intervals[i].end){//新区间的起点在此区间之间，终点超出此区间
                startflag = 1;
                temp.start  = intervals[i].start;
                
            }else if(startflag == 0  && i==len-1 && intervals[i].end< newInterval.start){//新区间在最后一个区间外
                result.push_back(intervals[i]);
                result.push_back(newInterval);
                return result;    
            }

            if(startflag==1 && endflag==0 && i==len-1 && newInterval.end >intervals[i].end){//新区间的终点在最后一个区间之后
                temp.end = newInterval.end;
                endflag = 1;
                i++;
                result.push_back(temp);
                return result; 
                
            }else if(startflag==1 && endflag==0 && newInterval.end > intervals[i].end){//新区间的终点越过此区间
                i++;
                continue;
            }else if(startflag==1 && endflag==0 && newInterval.end < intervals[i].start){//新区间的终点在此区间之前
               endflag = 1;
               temp.end = newInterval.end;
               result.push_back(temp);
               break;
            }else if(startflag==1 && endflag==0 && newInterval.end >= intervals[i].start &&
                newInterval.end <= intervals[i].end){//新区间的终点在此区间之间
                endflag = 1;
                temp.end = intervals[i].end;
                i++;
                result.push_back(temp);
                break;
            }
        }//end for
                    
        while(i<len){
           result.push_back(intervals[i++]);
        }
        return result;
    }//end func
};