网络流模板
1.dinic
板子错坑死人啊
1 #include<cstdio> 2 #include<iostream> 3 #include<cstdlib> 4 #include<cstring> 5 #include<algorithm> 6 #include<cmath> 7 #include<queue> 8 #define maxn 10002 9 #define maxm 100002 10 #define inf 1e9 11 using namespace std; 12 int n,m,cur[maxn],tot=1,head[maxn]; 13 int S,T,ans,d[maxn]; 14 struct node 15 { 16 int cap,nex,v; 17 }e[maxm*2]; 18 void lj(int t1,int t2,int t3){ 19 e[++tot].v=t2;e[tot].cap=t3;e[tot].nex=head[t1];head[t1]=tot; 20 } 21 bool BFS() 22 { 23 queue<int>q; 24 for(int i=1;i<=n;i++)d[i]=inf; 25 q.push(S);d[S]=0; 26 while(!q.empty()) 27 { 28 int x=q.front();q.pop();cur[x]=head[x]; 29 for(int i=head[x];i;i=e[i].nex){ 30 if(d[e[i].v]>d[x]+1&&e[i].cap>0){ 31 d[e[i].v]=d[x]+1; 32 q.push(e[i].v); 33 } 34 } 35 } 36 return d[T]!=inf; 37 } 38 int lian(int k,int a) 39 { 40 if(k==T||!a)return a; 41 int f,flow=0; 42 for(int &i=cur[k];i;i=e[i].nex){ 43 if(d[e[i].v]==d[k]+1&&(f=lian(e[i].v,min(a,e[i].cap)))>0) 44 { 45 e[i].cap-=f;e[i^1].cap+=f; 46 a-=f;flow+=f; 47 } 48 if(!a)break; 49 } 50 return flow; 51 } 52 int main(){ 53 cin>>n>>m>>S>>T; 54 for(int i=1,t1,t2,t3;i<=m;i++){ 55 scanf("%d%d%d",&t1,&t2,&t3); 56 lj(t1,t2,t3);lj(t2,t1,0); 57 } 58 while(BFS())ans+=lian(S,inf); 59 printf("%d\n",ans); 60 return 0; 61 }
2.费用流
ek
1 #include<cstdio> 2 #include<iostream> 3 #include<cstdlib> 4 #include<cstring> 5 #include<algorithm> 6 #include<cmath> 7 #include<queue> 8 #define maxn 5005 9 #define inf 1e9 10 using namespace std; 11 int n,m,S,T,head[maxn],tot=1; 12 int d[maxn],flag[maxn],pre[maxn],f,ans; 13 struct node{ 14 int v,nex,cap,w; 15 }e[maxn*20]; 16 void add(int t1,int t2,int t3,int t4){ 17 e[++tot].v=t2;e[tot].cap=t3;e[tot].w=t4;e[tot].nex=head[t1];head[t1]=tot; 18 } 19 bool mcf(){ 20 queue<int>q;q.push(S); 21 for(int i=1;i<=n;i++)d[i]=inf;d[S]=0; 22 while(!q.empty()){ 23 int k=q.front();q.pop(); 24 for(int i=head[k];i;i=e[i].nex){ 25 if(d[e[i].v]>d[k]+e[i].w&&e[i].cap){ 26 d[e[i].v]=d[k]+e[i].w; 27 pre[e[i].v]=i; 28 if(!flag[e[i].v])flag[e[i].v]=1,q.push(e[i].v); 29 } 30 } 31 flag[k]=0; 32 } 33 if(d[T]==inf)return 0; 34 int M=inf,sum=0; 35 for(int i=T;i!=S;i=e[pre[i]^1].v){ 36 M=min(M,e[pre[i]].cap),sum+=e[pre[i]].w; 37 } 38 f+=M,ans+=sum*M; 39 40 for(int i=T;i!=S;i=e[pre[i]^1].v){ 41 e[pre[i]].cap-=M;e[pre[i]^1].cap+=M; 42 } 43 return 1; 44 } 45 int main(){ 46 scanf("%d%d%d%d",&n,&m,&S,&T); 47 for(int i=1,t1,t2,t3,t4;i<=m;i++){ 48 scanf("%d%d%d%d",&t1,&t2,&t3,&t4); 49 add(t1,t2,t3,t4);add(t2,t1,0,-t4); 50 } 51 while(mcf()); 52 cout<<f<<' '<<ans<<endl; 53 return 0; 54 }
zkw
1 #include<cstdio> 2 #include<iostream> 3 #include<cstdlib> 4 #include<cstring> 5 #include<algorithm> 6 #include<cmath> 7 #include<queue> 8 #define maxn 5005 9 #define inf 1e9 10 using namespace std; 11 int flag[maxn],d[maxn],head[maxn],cur[maxn],tot=1; 12 int n,m,S,T,ans; 13 struct node{ 14 int v,nex,cap,w; 15 }e[maxn*20]; 16 void add(int t1,int t2,int t3,int t4){ 17 e[++tot].v=t2;e[tot].cap=t3;e[tot].w=t4;e[tot].nex=head[t1];head[t1]=tot; 18 } 19 bool spfa(){ 20 for(int i=1;i<=n;i++)d[i]=inf,flag[i]=0; 21 queue<int>q;q.push(S);d[S]=0;flag[S]=1; 22 while(!q.empty()){ 23 int k=q.front();q.pop(); 24 for(int i=head[k];i;i=e[i].nex){ 25 if(e[i].cap&&d[e[i].v]>d[k]+e[i].w){ 26 d[e[i].v]=d[k]+e[i].w; 27 if(!flag[e[i].v]){ 28 flag[e[i].v]=1;q.push(e[i].v); 29 } 30 } 31 } 32 flag[k]=0; 33 } 34 return d[T]!=inf; 35 } 36 int lian(int k,int a){ 37 flag[k]=1; 38 if(k==T||!a)return a; 39 int flow=0; 40 for(int &i=cur[k];i;i=e[i].nex){ 41 if(d[e[i].v]==d[k]+e[i].w&&e[i].cap&&!flag[e[i].v]){ 42 int f=lian(e[i].v,min(e[i].cap,a)); 43 e[i].cap-=f;e[i^1].cap+=f; 44 flow+=f;a-=f; 45 ans+=f*e[i].w; 46 }if(!a)break; 47 } 48 return flow; 49 } 50 int main(){ 51 cin>>n>>m>>S>>T; 52 for(int i=1,t1,t2,t3,t4;i<=m;i++){ 53 scanf("%d%d%d%d",&t1,&t2,&t3,&t4); 54 add(t1,t2,t3,t4);add(t2,t1,0,-t4); 55 } 56 int F=0; 57 while(spfa()){ 58 flag[T]=1; 59 while(flag[T]){ 60 for(int i=1;i<=n;i++)flag[i]=0,cur[i]=head[i]; 61 F+=lian(S,inf); 62 } 63 } 64 cout<<F<<' '<<ans<<endl; 65 return 0; 66 }
