bzoj1834 [ZJOI2010]network 网络扩容

　　第一问跑最大流，第二问新建一条边连接0和1，流量为上第一问的答案+k,费用为0，接下来图中每条边拆成两条边，第一条容量为C费用为0，第二条容量无穷费用为W，再跑一遍费用流即可。

　　代码

 #include<cstdio>
 #include<algorithm>
 #include<cstring>
 #include<iostream>
 #include<set>
 #include<queue>
 #define mp make_pair
 #define inf 0x37373737
 #define N 30050
 #define M 30050
 using namespace std;
 struct Dinic {
     int s, t, n, pre[N], cur[N], h[N], level[N], sign, q[N];
     int cap[M], to[M], ne[M], flow, e;
     void liu(int u, int v, int w) {
         to[e] = v, ne[e] = h[u], cap[e] = w;
         h[u] = e++;
     }
     void link(int u, int v, int w) {
         liu(u, v, w);
         liu(v, u, );
     }
     void init(int n) {
         for (int i = ; i <= n; ++i)
             h[i] = -;
         e = ;
     }
     bool bfs() {
         int L = , R = ;
         fill(level, level + n, -);
         sign = q[R++] = t;
         level[t] = ;
         while (L < R && level[s] == -) {
             int c = q[L++];
             for (int k = h[c]; ~k; k = ne[k]) {
                 if (cap[k ^ ] >  && level[to[k]] == -)
                     level[to[k]] = level[c] + , q[R++] = to[k];
             }
         }
         return ~level[s];
     }
     void push() {
         int pl = inf, p, k;
         for (p = t; p != s; p = to[k ^ ]) {
             k = pre[p];
             pl = min(pl, cap[k]);
         }
         for (p = t; p != s; p = to[k ^ ]) {
             k = pre[p];
             cap[k] -= pl;
             cap[k ^ ] += pl;
             if (cap[k] == )
                 sign = to[k ^ ];
         }
         flow += pl;
     }
     void dfs(int c) {
         if (c == t)
             push();
         else {
             for (int &k = cur[c]; ~k; k = ne[k])
                 if (cap[k] >  && level[to[k]] +  == level[c]) {
                     pre[to[k]] = k;
                     dfs(to[k]);
                     if (level[sign] > level[c])
                         return;
                     sign = t;
                 }
             level[c] = -;
         }
     }
     int run(int _s, int _t, int _n) {
         s = _s, t = _t, n = _n;
         flow = ;
         while (bfs()) {
             for (int i = ; i < n; ++i)
                 cur[i] = h[i];
             dfs(s);
         }
         return flow;
     }
 } mf;
 
  struct MCMF{
     int h[N] , dis[N] , ing[N] , pre[N] , s , t , n;
     int to[M] , ne[M] , cap[M] , cost[M] , e;
     void ini(){
         fill(h,h+N,-);
         e = ;
     }
     void liu(int u,int v,int c,int w){
         to[e] = v , ne[e] = h[u] , cap[e] = c , cost[e] = w;
         h[u] = e++;
     }
     void link(int u,int v,int c,int w){
         liu(u,v,c,w);
         liu(v,u,,-w);
     }
     bool spfa(){
         queue<int> Q;
         fill(ing,ing+n,);
         fill(pre,pre+n,-);
         fill(dis,dis+n,inf);
         ing[s] = true , dis[s] = ;
         Q.push(s);
         while(!Q.empty()){
             int c = Q.front();Q.pop();ing[c] = false;
             for(int k=h[c];~k;k=ne[k]){
                 int v = to[k];
                 if(cap[k] <= ) continue;
                 if(dis[c] +  cost[k] < dis[v]){
                     dis[v] = dis[c] + cost[k];
                     pre[v] = k;
                     if(!ing[v]) Q.push(v) , ing[v] = true;
                 }
             }
         }
         return dis[t] != inf;
     }
     int flow , mincost;
     pair<int,int> run(int _s,int _t,int _n){
         s = _s , t = _t , n = _n;
         flow = mincost = ;
         while(spfa()){
             int pl = inf , p , k;
             for(p=t;p!=s;p=to[k^]){
                 k = pre[p];
                 pl = min(pl,cap[k]);
             }
             for(p=t;p!=s;p=to[k^]){
                 k = pre[p];
                 cap[k] -= pl;
                 cap[k^] += pl;
             }
             mincost += pl * dis[t];
             flow += pl;
         }
         return mp(flow,mincost);
     }
 };
 MCMF mcmf;
 
 int n,m,k,i,a,b,c,d,flow,cost;
 int main()
 {
     scanf("%d%d%d",&n,&m,&k);
     mf.init(n+);
     mcmf.ini();
     for (i=;i<=m;i++)
     {
         scanf("%d%d%d%d",&a,&b,&c,&d);
         mf.link(a,b,c);
         mcmf.link(a,b,c,);
         mcmf.link(a,b,,d);
     }
     flow=mf.run(,n,n+);
     mcmf.link(,,flow+k,);
     printf("%d %d",flow,mcmf.run(,n,n+).second);
 }