The 2019 China Collegiate Programming Contest Harbin Site A. Artful Paintings 差分约束模板

#include
using namespace std;
const int N=3010;
const int INF=1e9;
int dist[N];
struct node{
	int u,v,cost;
};
struct node2{
	int l,r,k;
};
vector<node>E;
vector<node2>g1,g2;
bool bf(int st,int n){
	for(int i=1;i<=n;i++) dist[i]=INF;
	dist[st]=0;
	for(int i=1;i<=n;i++){
		bool fl=false;
		for(int j=0;j<E.size();j++){
			int u=E[j].u,v=E[j].v,cost=E[j].cost;
			if(dist[v]>dist[u]+cost){
				dist[v]=dist[u]+cost;
				if(dist[v]<0) return false;
				fl=true;
			}
		}
		if(!fl) return true;
	}
	for(int j=0;j<E.size();j++){
		if(dist[E[j].v]>dist[E[j].u]+E[j].cost){
			return false;
		}
	}
	return true;
}
int t,n,m1,m2;
int main(){
	scanf("%d",&t);
	while(t--){
		E.clear();g1.clear();g2.clear();
		scanf("%d%d%d",&n,&m1,&m2);
		for(int i=1;i<=m1;i++){
			int l,r,k;scanf("%d%d%d",&l,&r,&k);
			g1.push_back({l,r,k});
		}
		for(int i=1;i<=m2;i++){
			int l,r,k;scanf("%d%d%d",&l,&r,&k);
			g2.push_back({l,r,k});
		}
		int l=0,r=n,ans=0;
		while(l<r){
			int mid=(l+r)/2;
			E.clear();
			for(int i=1;i<=n;i++){
				E.push_back({i-1,i,1});
				E.push_back({i,i-1,0});
			}
			E.push_back({0,n,mid});
			E.push_back({n,0,-mid});
			for(int i=0;i<m1;i++) E.push_back({g1[i].r,g1[i].l-1,-g1[i].k});
			for(int i=0;i<m2;i++) E.push_back({g2[i].l-1,g2[i].r,mid-g2[i].k});
			if(bf(0,n)) r=mid;
			else l=mid+1;
		}
		cout<<l<<endl;
	}
}