http://ybt.ssoier.cn:8088/problem_show.php?pid=1509

#include <bits/stdc++.h>
using namespace std;
const int N = 5e4 + 10;
const int INF = 0x3f3f3f3f;

int n;
int u , v , w , maxx;
vector<pair<int,int> > vc[N];
int dis[N];
bool vis[N];
void spfa()//求最长路！！！ 
{
	memset(dis, -INF, sizeof(dis));
	dis[0] = 0;
	vis[0] = 1;//表示当前点是否在队列中 
	queue<int> q;
	q.push(0);
	
	while(!q.empty())
	{
		int u = q.front();
		q.pop();
		vis[u] = 0;
		for(int i = 0; i < vc[u].size(); i++)
		{
			int v = vc[u][i].first , w = vc[u][i].second;
			if(dis[v] < dis[u] + w)
			{
				dis[v] = dis[u] +w;
				if(!vis[v]) 
				{
					q.push(v);	
					vis[v] = 1;
				}
			}	
		} 
	}
}

int main()
{
	cin >> n;
	for(int i = 1; i <= n; i++)
	{
		cin >> u >> v >> w;
		u++ , v++;//整体右移 
		//sum[v] - sum[u - 1] >= w
		vc[u - 1].push_back({v , w});
		maxx = max(maxx , v);
	}
	
	//隐藏不等式 sum[i] - sum[i - 1] >= 0     sum[i - 1] - sum[i] >= -1
	for(int i = 1; i <= maxx; i++)
	{
		vc[i - 1].push_back({i , 0});	
		vc[i].push_back({i - 1, -1});	
	} 
	spfa();
	cout << dis[maxx];
	return 0;
}