LightOJ1074（spfa+dfs标记负环及负环能够到达的点）

#include<cstdio>
#include<cstring>
#include<cmath>
#include<queue>
#include<algorithm>
using namespace std;

const int maxn=205;
const int maxm=40005;
const int inf=0x3f3f3f3f;
int T,cas,n,m,q,cnt,loop,bn[maxn],head[maxn],vis[maxn],dis[maxn],upd[maxn];
int f[maxn];

struct node{
    int v,w,nex;
}edge[maxm];

void adde(int u,int v,int w){
    edge[++cnt].v=v;
    edge[cnt].w=w;
    edge[cnt].nex=head[u];
    head[u]=cnt;
}

void dfs(int u){
    for(int i=head[u];i;i=edge[i].nex){
        int v=edge[i].v;
        if(f[v]) continue;
        f[v]=1;
        dfs(v);
    }
}

void spfa(){
    queue<int> que;
    for(int i=1;i<=n;++i)
        vis[i]=0,dis[i]=inf,upd[i]=0,f[i]=0;
    que.push(1);
    vis[1]=1,dis[1]=0,upd[1]=1;
    while(!que.empty()){
        int u=que.front();que.pop();
        vis[u]=0;
        if(f[u]) continue;
        for(int i=head[u];i;i=edge[i].nex){
            int v=edge[i].v,w=edge[i].w;
            if(dis[v]>dis[u]+w){
                dis[v]=dis[u]+w;
                if(!vis[v]){
                    ++upd[v];
                    if(upd[v]>n){
                        f[u]=1;
                        dfs(u);
                    }
                    else{
                        vis[v]=1;
                        que.push(v);
                    }
                }
            }
        }
    }
}

int main(){
    scanf("%d",&T);
    while(T--){
        printf("Case %d:\n",++cas);
        scanf("%d",&n);
        cnt=0;
        for(int i=1;i<=n;++i)
            head[i]=0;
        for(int i=1;i<=n;++i)
            scanf("%d",&bn[i]);
        scanf("%d",&m);
        for(int i=1;i<=m;++i){
            int u,v;
            scanf("%d%d",&u,&v);
            adde(u,v,(bn[v]-bn[u])*(bn[v]-bn[u])*(bn[v]-bn[u]));
        }
        spfa();
        scanf("%d",&q);
        for(int i=1;i<=q;++i){
            int tmp;
            scanf("%d",&tmp);
            if(f[tmp]||dis[tmp]==inf||dis[tmp]<3)
                printf("?\n");
            else
                printf("%d\n",dis[tmp]);
        }
    }
    return 0;
}