ACM圖論模板

//費用流模板
struct Edge
{
    int u,v,c,f,cost;
    Edge(){}
    Edge(int x,int y,int up,int flow,int co)
    {
        u=x,v=y,c=up,f=flow,cost=co;
    }
};
struct MCMF
{
    int ecnt,head[maxm],next[maxm*maxm];
    int s,t,dist[maxm],vis[maxm],a[maxm];
    int pre[maxm];
    queue<int >Q;
    Edge edges[maxm*maxm];
    void init(int T)
    {
        s=0,t=T;
        ecnt=0;
        for (int i =0;i<=T;i++)head[i]=-1;
    }
    void addedge(int u,int v,int c,int cost)
    {
        edges[ecnt]=Edge(u,v,c,0,cost);
        next[ecnt]=head[u];
        head[u]=ecnt++;
        edges[ecnt]=Edge(v,u,0,0,-cost);
        next[ecnt]=head[v];
        head[v]=ecnt++;
    }
    bool spfa(int &flow,int &cost)
    {
        for (int i=0;i<=t;i++)dist[i]=INF,vis[i]=0,a[i]=INF;
        dist[0]=0;
        Q.push(0);
        while (!Q.empty())
        {
            int u=Q.front();
            Q.pop();
            vis[u]=0;
            for (int i=head[u];i!=-1;i=next[i])
            {
                Edge e=edges[i];
                if (e.c>e.f&&dist[e.v]>dist[u]+e.cost)
                {
                    dist[e.v]=dist[u]+e.cost;
                    a[e.v]=min(a[u],e.c-e.f);
                    pre[e.v]=i;
                    if (!vis[e.v])
                    {
                        vis[e.v]=1;
                        Q.push(e.v);
                    }
                }
            }
        }
        if (dist[t]==INF)return 0;
        flow+=a[t];
        cost+=a[t]*dist[t];
        int u=t;
        while (1)
        {
            edges[pre[u]].f+=a[t];
            edges[pre[u]^1].f-=a[t];
            u=edges[pre[u]].u;
            if (u==s)
                break;
        }
        return 1;
    }
    int slove()
    {
        int flow=0,cost=0;
        while (spfa(flow,cost));
        return cost;
    }
}slove;

//網絡流模板,有上下界，建圖方式

struct Edge{
    int start,to,cap,blow,flow;
    Edge(){}
    Edge(int u,int v,int c,int b,int f){
        start=u,to=v,cap=c,blow=b,flow=f;
    }
};
struct Dinic{
    vector<Edge >edges;
    vector<int >G[maxn];
    int s,t,cur[maxn],d[maxn];
    bool vis[maxn];
    void init(int n){
        this->s=0,this->t=n;
        edges.clear();
        for (int i = 0; i <= n; i++){
            G[i].clear();
        }
    }
    void addedge(int u,int v,int b,int c){
        edges.push_back(Edge(u,v,c-b,b,0));
        edges.push_back(Edge(v,u,0,0,0));
        G[u].push_back(edges.size()-2);
        G[v].push_back(edges.size()-1);
    }
    bool bfs(){
        queue<int >Q;
        memset(vis,0,sizeof(vis));
        d[s]=0;
        Q.push(s);
        vis[s]=1;
        while (!Q.empty()){
            int u=Q.front();
            Q.pop();
            for (int i = 0;i < G[u].size(); i++){
                Edge e=edges[G[u][i]];
                if (e.cap>e.flow&&!vis[e.to]){
                    vis[e.to]=1;
                    d[e.to]=d[u]+1;
                    Q.push(e.to);
                }
            }
        }
        return vis[t];
    }
    int dfs(int u,int x){
        if (u==t||x==0)return x;
        int f = 0,flow = 0;
        for (int &i = cur[u];i < G[u].size(); i++){
            int j = G[u][i];
            Edge e=edges[j];
            if (d[u]+1 == d[e.to] && (f=dfs(e.to,min(e.cap-e.flow,x))) > 0){
                edges[j].flow+=f;
                edges[j^1].flow-=f;
                flow+=f;
                x-=f;
                if (x==0)break;;
            }
        }
        return flow;
    }
    bool slove(){
        int flow = 0;
        while (bfs()){
            memset(cur,0,sizeof(cur));
            flow += dfs(s,INF);
        }
        for (int i = 0;i < edges.size();i += 2){
            Edge e=edges[i];
            if ((e.start == s || e.to == t) && e.cap != e.flow){
                return 0;
            }
        }
   <span style="white-space:pre">	</span>return 1;
    }
}slove;
int main()
{
    int n,m;
    while (scanf("%d%d",&n,&m)!=EOF)
    {
        int i,j,u,v,c,b;
        memset(in,0,sizeof(in));
        memset(out,0,sizeof(out));
        slove.init(n+1);
        for (i=0;i<m;i++){
            scanf("%d%d%d%d",&u,&v,&b,&c);
            slove.addedge(u,v,b,c);
            in[v]+=b;
            out[u]+=b;
        }
        for (i=1;i<=n;i++){
            if (in[i]>out[i]){
                slove.addedge(0,i,0,in[i]-out[i]);  
            }
            else if (in[i]<out[i]){
                slove.addedge(i,n+1,0,out[i]-in[i]);
            }
        }
        if (slove.slove())continue;
        puts("NO");
    }
    return 0;
}

二分圖最優匹配
bool dfs(int u){
    sx[u]=1;
    for (int v = 1; v <= n; v++){
        if ( G[u][v] == lx[u] + ly[v]){
            if (sy[v])continue;
            sy[v]=1;
            if (match[v] == 0 || dfs(match[v])){
                match[v] = u;
                return 1;
            }
        }
        else{
            slack = min(slack , lx[u] + ly[v] - G[u][v]);
        }
    }
    return 0;
}
void slove()
{
    slack = INF ;
    for (int u = 1; u <= n; ++u){
        while (1){
            slack = INF;
            for (int i = 1; i <= n; ++i){
                sx[i] = sy[i] = 0;
            }
            if (dfs(u))break;
            for (int i = 1; i <= n; ++i){
                if (sx[i])lx[i] -= slack;
                if (sy[i])ly[i] += slack;
            }
        }
    }
}