There are several activities, the ith start time and end time are [Si, fi), and the activities arranged in the same classroom cannot overlap. To arrange all activities, how many classrooms are required at least?
Input
A positive integer n (n <= 10000) in the first line represents the number of activities. Lines 2 to (n + 1) contain n start and end times. The start time is strictly less than the end time, and the times are all non-negative integers less than 1000000000
Output
A line contains an integer representing the minimum number of classrooms.
Input example
3 1 2 3 4 2 9
Output example
2
#include <iostream> #include <algorithm> #include <cstring> #include <cstdio> #include <vector> #include <queue> #include <stack> #include <cstdlib> #include <iomanip> #include <cmath> #include <cassert> #include <ctime> #include <map> #include <set> using namespace std; #pragma comment(linker, "/stck:1024000000,1024000000") #define lowbit(x) (x&(-x)) #define max(x,y) (x>=y?x:y) #define min(x,y) (x<=y?x:y) #define MAX 100000000000000000 #define MOD 1000000007 #define pi acos(-1.0) #define ei exp(1) #define PI 3.1415926535897932384626433832 #define ios() ios::sync_with_stdio(true) #define INF 0x3f3f3f3f #define mem(a) ((a,0,sizeof(a))) typedef long long ll; struct node { ll u,v; bool operator<(const node a) { return a.u==u?a.v>v:a.u>u; } }e[10006]; int n; int main() { scanf("%d",&n); for(int i=0;i<n;i++) scanf("%lld%lld",&e[i].u,&e[i].v); sort(e,e + n); priority_queue<int,vector<int>,greater<int> >q; ll end=e[0].v,pos=1; q.push(e[0].v); for(int i=1;i<n;i++) { if(e[i].u<q.top()) pos++; else q.pop(); q.push(e[i].v); } printf("%lld\n",pos); return 0; }