费用流+SPFA ||Luogu P3381【模板】最小费用最大流
题面：【模板】最小费用最大流
代码：
1 #include<cstdio> 2 #include<cstring> 3 #include<iostream> 4 #include<queue> 5 #define ll long long 6 #define min(a,b) ((a)<(b)?(a):(b)) 7 #define max(a,b) ((a)>(b)?(a):(b)) 8 using namespace std; 9 inline ll rd(){ 10 ll x=0,f=1;char c=getchar(); 11 while(c<'0'||c>'9'){if(c=='-')f=-1; c=getchar();} 12 while(c>='0'&&c<='9'){x=x*10+c-'0'; c=getchar();} 13 return f*x; 14 } 15 const int maxn=5050,maxm=50050; 16 int N,M,num_edge=-1,edge_head[maxn],S,T,u,v,w,f,pre[maxn]; 17 ll Dis[maxn],Fw[maxn],mxfw,mndis; 18 bool vis[maxn]; 19 queue<int>Q; 20 struct Edge{int to,nx,from;ll dis,fw;}edge[maxm<<1]; 21 inline void Add_edge(int from,int to,ll fw,ll dis){ 22 edge[++num_edge].nx=edge_head[from]; 23 edge[num_edge].from=from; 24 edge[num_edge].to=to; 25 edge[num_edge].fw=fw; 26 edge[num_edge].dis=dis; 27 edge_head[from]=num_edge; 28 return; 29 } 30 inline bool SPFA(){ 31 // for(int i=1;i<=N;i++) 32 // Dis[i]=Fw[i]=1ll<<60; 33 memset(Dis,0x7f,sizeof(Dis)); 34 memset(Fw,0x7f,sizeof(Fw)); 35 memset(vis,0,sizeof(vis)); 36 pre[S]=pre[T]=-1;//Imp 37 Q.push(S); 38 vis[S]=1; 39 Dis[S]=0; 40 while(!Q.empty()){ 41 int x=Q.front(); 42 Q.pop(); 43 vis[x]=0; 44 for(int i=edge_head[x];i!=-1;i=edge[i].nx){ 45 int y=edge[i].to; 46 if(edge[i].fw&&edge[i].dis+Dis[x]<Dis[y]){ 47 Dis[y]=edge[i].dis+Dis[x]; 48 Fw[y]=min(Fw[x],edge[i].fw);//这一步和Dinic差不多 49 pre[y]=i; 50 if(vis[y]==0){ 51 Q.push(y); 52 vis[y]=1; 53 } 54 } 55 } 56 } 57 if(pre[T]!=-1)return 1; 58 return 0; 59 } 60 inline void FYL(){ 61 mxfw=mndis=0; 62 while(SPFA()){ 63 mxfw+=Fw[T]; 64 mndis+=Dis[T]*Fw[T]; 65 for(int i=pre[T];i!=-1;i=pre[edge[i].from]){ 66 edge[i].fw-=Fw[T]; 67 edge[i^1].fw+=Fw[T]; 68 } 69 } 70 return; 71 } 72 int main(){ 73 memset(edge_head,-1,sizeof(edge_head)); 74 N=rd();M=rd();S=rd();T=rd(); 75 for(int i=1;i<=M;i++){ 76 u=rd();v=rd();w=rd();f=rd(); 77 Add_edge(u,v,w,f); 78 Add_edge(v,u,0,-f); 79 } 80 FYL(); 81 printf("%lld %lld\n",mxfw,mndis); 82 return 0; 83 }
By:AlenaNuna
