leetcode Merge Intervals & Insert Interval

Merge Intervals  是典型的贪心算法，通过对段进行开始时间排序，然后遍历，每次判断是否可以合并，如不可合并，则加入新的段

bool compare(const Interval &a,const Interval &b){
return (a.start<b.start);
}
class Solution {
public:
vector<Interval> merge(vector<Interval> &intervals) {
int len=intervals.size();
if(len<=1)return intervals;
vector<Interval>ans;
sort(intervals.begin(),intervals.end(),compare);
ans.push_back(intervals[0]);
for(int i=1;i<len;++i){
if(intervals[i].start<=ans[ans.size()-1].end){
if(intervals[i].end>ans[ans.size()-1].end)
ans[ans.size()-1].end=intervals[i].end;
}
else ans.push_back(intervals[i]);
}
return ans;
}
};与上一题差别不大，只需要稍加修改即可
class Solution {
public:
vector<Interval> insert(vector<Interval> &intervals, Interval newInterval) {
int len=intervals.size();
vector<Interval>ans;
if(len==0){ans.push_back(newInterval);return ans;}
//sort(intervals.begin(),intervals.end(),compare);
intervals.push_back(newInterval);
int i=len-1;
while(i>=0){
if(intervals[i].start>intervals[i+1].start){
Interval t=intervals[i+1];
intervals[i+1]=intervals[i];
intervals[i]=t;
i--;
}
else break;
}
ans.push_back(intervals[0]);
for(int i=1;i<=len;++i){
if(intervals[i].start<=ans[ans.size()-1].end){
if(intervals[i].end>ans[ans.size()-1].end)
ans[ans.size()-1].end=intervals[i].end;
}
else ans.push_back(intervals[i]);
}
return ans;
}
};