Tarjan+spfa,70pts求助
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Tarjan+spfa,70pts求助
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Alcl000000楼主2023/7/7 11:20

WA on #4,#5,#7(存图用的vector)

#include<bits/stdc++.h>
#define int long long
using namespace std;
struct node{
	long long x,y;
};
vector<long long> v[100005],vt[100005];
long long n,m;
long long dfn[100005],a[1000005],low[100005],co[1000005],ti,cnt,p[100005],r[100005],kkk=1;
stack <int> st;
void Tarjan(int u){
	st.push(u);
	dfn[u]=++ti;
	low[u]=dfn[u];
	for(int i=0;i<v[u].size();i++){
		int to=v[u][i];
		if(!dfn[to]){
			Tarjan(to);
			low[u]=min(low[u],low[to]);
		}else{
			if(!co[to]){
				low[u]=min(low[u],dfn[to]);
			}
		}
	}
	if(low[u]==dfn[u]){
		++cnt;
		co[u]=cnt;
		p[cnt]=a[u];
		while(st.top()!=u){
			int t=st.top();
			st.pop();
			co[t]=cnt;
			p[cnt]+=a[t];
		}
		st.pop();
	}
}
int vis[10005],dis[10005];
void spfa(){
	memset(dis,-0x3f,sizeof(dis));
	queue <int> q;
	q.push(kkk);
	vis[kkk]=1;
	dis[kkk]=p[kkk];
	while(!q.empty()){
		int now=q.front();
		q.pop();
		vis[now]=0;
		//		cout<<".";
		for(int i=0;i<vt[now].size();i++){
			int son=vt[now][i];
			if(dis[son]<dis[now]+p[son]){
				dis[son]=dis[now]+p[son];
				if(!vis[son]){
					vis[son]=1;
					//cout<<".";
					q.push(son);
				}
			}
		}
	}
}
signed main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	for(int i=1;i<=m;i++){
		int x,y,z;
		cin>>x>>y;
		v[x].push_back(y);
	}
	for(int i=1;i<=n;i++){
		if(!dfn[i]) Tarjan(i);
	}
	for(int i=1;i<=n;i++){
		for(int j=0;j<v[i].size();j++){
			if(co[i]!=co[v[i][j]]){
				vt[co[i]].push_back(co[v[i][j]]);
				r[co[v[i][j]]]++;
			}
			
		}
	//	cout<<endl;
	}
	for(int i=1;i<=cnt;i++){
//		cout<<r[i]<<endl;
		if(!r[i]){
			kkk=i;
			break;
		}
	}
//	cout<<kkk<<endl;
	spfa();
	int ma=-1000000;
	for(int i=1;i<=cnt;i++){
		ma=max(ma,dis[i]);
	}
	cout<<ma;
	return 0;
}

2023/7/7 11:20
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