区间合并

 1 #include <iostream>
 2 #include <algorithm>
 3 #include <vector>
 4 #include <climits>
 5 
 6 using namespace std;
 7 
 8 const int N = 1e5+10;
 9 vector<pair<int, int> > interval;//存储所有区间
10 int n;
11 
12 void merge_interval(vector<pair<int, int> >& tmp){
13     sort(tmp.begin(), tmp.end());//pair类型排序先按first排序，再按照second排序
14     
15     vector<pair<int, int> > ans;
16     
17     int l = INT_MIN, r = INT_MIN;//相当于增加一个虚拟区间
18     
19     for(auto intex : tmp){
20         //没有交集
21         if(intex.first > r){
22             if(l != INT_MIN && r != INT_MIN) ans.push_back({l, r});
23             l = intex.first;
24             r = intex.second;
25         }else
26             //有交集
27             r = max(r,intex.second);
28     }
29     
30     if(l != INT_MIN && r != INT_MIN)ans.push_back({l, r});
31     
32     interval = ans;
33 }
34 
35 int main(){
36     cin >> n;
37     for(int i = 0;i < n;++i){
38         int l, r;
39         cin >> l >> r;
40         interval.push_back({l, r});
41     }
42     //区间合并
43     merge_interval(interval);
44     
45     cout << interval.size() << endl;
46     
47     return 0;
48 }