Bellman-Ford最短路

//队列优化 O（E*N）
struct Edge{
    int from,to,dist;
    Edge(int u,int v,int d):from(u),to(v),dist(d){}
};

struct BellmanFord{
    int n,m;
    vector<Edge> edges;
    vector<int> G[maxn];
    bool inq[maxn];
    int d[maxn];
    int p[maxn];
    int cnt[maxn];
    
    void init(int n){
        this->n=n;
        edges.clear();
        for(int i=0;i<n;i++) G[i].clear();
    }
    
    void AddEdge(int from,int to,int dist){
        edges.push_back(Edge(from,to,dist));
        m=edges.size();
        G[from].push_back(m-1);
    }
    
    bool negativeCycle(){
        queue<int> Q;
        memset(inq,0,sizeof(inq));
        memset(cnt,0,sizeof(cnt));
        for(int i=0;i<n;i++) d[i]=0,inq[i]=true,Q.push(i);
        while(!Q.empty()){
            int u=Q.front();Q.pop();
            inq[u]=false;
            for(int i=0;i<G[u].size();i++){
                Edge& e=edges[G[u][i]];
                if(d[e.to]>d[u]+e.dist){
                    d[e.to]=d[u]+e.dist;
                    p[e.to]=G[u][i];
                    if(!inq[e.to]){
                        Q.push(e.to);
                        inq[e.to]=true;
                        if(++cnt[e.to]>n) return false;
                    }
                }
            }
        }
        return true;
    }
};