区间选点

#include <iostream>
#include <algorithm>
using namespace std;
const int maxm = 5000 + 10;
const int maxn = 3e4 + 10;
struct node{
	int s,t,num;
}a[maxm];
int n,m;
bool vis[maxn];
bool cmp(node a,node b){
	return a.t<b.t;
}
int solve(){
	sort(a+1,a+m+1,cmp);
	int sum = 0;
	for(int i = 1;i<=m;i++){  //枚举每个活动
		int k = 0;
		for(int j = a[i].s;j<=a[i].t;j++)
			if(vis[j]) k++;   //已经种了多少
		if(k>=a[i].num) continue;
		for(int j = a[i].t;j>=a[i].s;j--)  //插入后面
			if(!vis[j]){
				vis[j] = true;
				k++;
				sum++;
				if(k==a[i].num) break;
			}
	}
	return sum; 
}
int main()
{
 	cin>>n>>m;
 	for(int i = 1;i<=m;i++)
 		cin>>a[i].s>>a[i].t>>a[i].num;
 	cout<<solve()<<endl;
	return 0;
}