LeetCode: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].

题目：插入新区间

思路：感觉这个题做起来比看起来复杂很多。。逻辑上情况比较多，我是遍历给定区间，根据新区间的 start 和 end 相对于当前区间的位置关系，分别处理。特别想说的是：研究了一下用 iterator 遍历 vector，感觉就是个坑，做 insert 、 push_back 、 erase 操作之后需要重新指定 iterator ，好麻烦。最后还是选用下标访问 vector 的方式。标志 isstart 和 isend 用来标记是否处理好新区间的 start / end。另外要考虑清楚插入区间的位置，插入后遍历下标也做相应移动即可。

 

 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> insert(vector<Interval>& intervals, Interval newInterval) {13         Interval addinterval;14         bool isstart = false;15         bool isend = false;16         if(!intervals.size()){17             intervals.push_back(newInterval);18             return intervals;19         }20         if(newInterval.start <= intervals[0].start && newInterval.end >= intervals[intervals.size()-1].end){21             vector<Interval> ret;22             ret.push_back(newInterval);23             return ret;24         }25         for(int i = 0;i<intervals.size();){26             if(newInterval.start < intervals[i].start){27                 if(newInterval.end < intervals[i].start){28                     if(!isend){29                         if(!isstart){30                             intervals.insert(intervals.begin()+i, newInterval);31                             isstart = true;32                             isend = true;33                             i+=2;34                         }35                         else{36                             addinterval.end = newInterval.end;37                             intervals.insert(intervals.begin()+i, addinterval);38                             isend = true;39                             break;40                         }41                     }42                     else{43                         break;44                     }45                 }else if(newInterval.end < intervals[i].end){46                     if(!isstart){47                         addinterval.start = newInterval.start;48                         addinterval.end = intervals[i].end;49                         intervals.insert(intervals.begin()+i, addinterval);50                         i++;51                         isstart = true;52                         isend = true;53                         intervals.erase(intervals.begin() + i);54                         break;55                     }else{56                         if(!isend){57                             addinterval.end = intervals[i].end;58                             intervals.insert(intervals.begin()+i, addinterval);59                             i++;60                             isend = true;61                             intervals.erase(intervals.begin() + i);62                         }63                     }64                 }else{65                     intervals.erase(intervals.begin() + i);66                 }67             }else if(newInterval.start <= intervals[i].end){68                 if(newInterval.end <= intervals[i].end){69                     isstart = true;70                     isend = true;71                     break;72                 }else{73                     addinterval.start = intervals[i].start;74                     isstart = true;75                     intervals.erase(intervals.begin() + i);76                 }77             }else{78                 i++;79             }80         }81         82         if(!isstart){83             intervals.push_back(newInterval);84             return intervals;85         }86         if(!isend){87             addinterval.end = newInterval.end;88             intervals.push_back(addinterval);89             return intervals;90         }91         return intervals;92     }93 };