有上下界的网络流问题
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这个博客写的不错：http://www.cnblogs.com/kane0526/archive/2013/04/05/3001108.html
1 #include<cstdio> 2 #include<iostream> 3 #include<cmath> 4 #include<cstring> 5 #include<algorithm> 6 using namespace std; 7 char ch; 8 bool ok; 9 void read(int &x){ 10 for (ok=0,ch=getchar();!isdigit(ch);ch=getchar()) if (ch==‘-‘) ok=1; 11 for (x=0;isdigit(ch);x=x*10+ch-‘0‘,ch=getchar()); 12 if (ok) x=-x; 13 } 14 const int maxn=205; 15 const int maxm=maxn*maxn; 16 const int inf=1061109567; 17 int n,m,a,b,c,d; 18 struct flow{ 19 int tot,id,s,t,maxflow,now[maxn],son[maxm],pre[maxm],val[maxm],down[maxm],up[maxm],sum[maxn]; 20 int head,tail,que[maxn],dis[maxn]; 21 bool bo[maxn]; 22 void init(){tot=1,s=0,t=n+1,memset(now,0,sizeof(now));} 23 void put(int a,int b,int c){pre[++tot]=now[a],now[a]=tot,son[tot]=b,val[tot]=c;} 24 void add(int a,int b,int c){put(a,b,c),put(b,a,0);} 25 void add(int a,int b,int c,int d){down[++id]=c,up[id]=d,sum[a]-=c,sum[b]+=c,add(a,b,d-c);} 26 void prepare(){ 27 for (int i=1;i<=n;i++) if (sum[i]>0) add(s,i,sum[i]),maxflow+=sum[i]; else add(i,t,-sum[i]); 28 } 29 bool bfs(){ 30 memset(bo,0,sizeof(bo)); 31 memset(dis,0,sizeof(dis)); 32 head=0,tail=1,que[1]=s,bo[s]=1; 33 while (head<tail){ 34 int u=que[++head]; 35 for (int p=now[u],v=son[p];p;p=pre[p],v=son[p]) 36 if (val[p]&&!bo[v]) bo[v]=1,dis[v]=dis[u]+1,que[++tail]=v; 37 } 38 return bo[t]; 39 } 40 int dfs(int u,int rest){ 41 if (u==t) return rest; 42 int ans=0; 43 for (int p=now[u],v=son[p];p&&rest;p=pre[p],v=son[p]) 44 if (val[p]&&dis[v]==dis[u]+1){ 45 int d=dfs(v,min(rest,val[p])); 46 val[p]-=d,val[p^1]+=d,rest-=d,ans+=d; 47 } 48 if (!ans) dis[u]=-1; 49 return ans; 50 } 51 int dinic(){ 52 int ans=0; 53 while (bfs()) ans+=dfs(s,inf); 54 return ans; 55 } 56 void work(){ 57 if (maxflow!=dinic()){puts("NO");return;} 58 puts("YES"); 59 for (int i=1;i<=m;i++) printf("%d\\n",val[(i<<1)+1]+down[i]); 60 } 61 }f; 62 int main(){ 63 read(n),read(m),f.init(); 64 for (int i=1;i<=m;i++) read(a),read(b),read(c),read(d),f.add(a,b,c,d); 65 f.prepare(),f.work(); 66 return 0; 67 }
1 #include<cstdio> 2 #include<iostream> 3 #include<cmath> 4 #include<cstring> 5 #include<algorithm> 6 using namespace std; 7 char ch; 8 bool ok; 9 void read(int &x){ 10 for (ok=0,ch=getchar();!isdigit(ch);ch=getchar()) if (ch==‘-‘) ok=1; 11 for (x=0;isdigit(ch);x=x*10+ch-‘0‘,ch=getchar()); 12 if (ok) x=-x; 13 } 14 const int maxn=1400; 15 const int maxm=740000; 16 const int inf=1061109567; 17 int n,m,a,b,c,d,x,y; 18 bool flag[maxm]; 19 struct flow{ 20 int s[2],t[2],tot,id,now[maxn],son[maxm],pre[maxm],val[maxm],down[maxm],sum[maxn]; 21 int head,tail,que[maxn],dis[maxn]; 22 bool bo[maxn]; 23 void init(){s[0]=0,t[0]=n+m+1,s[1]=n+m+2,t[1]=n+m+3,tot=1,id=0,memset(now,0,sizeof(now)),memset(sum,0,sizeof(sum));} 24 void put(int a,int b,int c){pre[++tot]=now[a],now[a]=tot,son[tot]=b,val[tot]=c;} 25 void add(int a,int b,int c){put(a,b,c),put(b,a,0);} 26 void add(int a,int b,int c,int d){sum[a]-=c,sum[b]+=c,down[++id]=c,add(a,b,d-c);} 27 bool bfs(int op){ 28 memset(bo,0,sizeof(bo)); 29 memset(dis,0,sizeof(dis)); 30 head=0,tail=1,bo[s[op]]=1,que[1]=s[op]; 31 while (head<tail){ 32 int u=que[++head]; 33 for (int p=now[u],v=son[p];p;p=pre[p],v=son[p]) 34 if (val[p]&&!bo[v]){ 35 if (!op&&(v==s[1]||v==t[1]||(p>>1)==id+1)) continue; 36 bo[v]=1,dis[v]=dis[u]+1,que[++tail]=v; 37 } 38 } 39 return bo[t[op]]; 40 } 41 int dfs(int u,int rest,int op){ 42 if (u==t[op]) return rest; 43 int ans=0; 44 for (int p=now[u],v=son[p];p&&rest;p=pre[p],v=son[p]) 45 if (val[p]&&dis[v]==dis[u]+1){ 46 if (!op&&(v==s[1]||v==t[1]||(p>>1)==id+1)) continue; 47 int d=dfs(v,min(val[p],rest),op); 48 val[p]-=d,val[p^1]+=d,ans+=d,rest-=d; 49 } 50 if (!ans) dis[u]=-1; 51 return ans; 52 } 53 int dinic(int op){ 54 int ans=0; 55 while (bfs(op)) ans+=dfs(s[op],inf,op); 56 return ans; 57 } 58 void work(){ 59 add(t[0],s[0],inf); 60 int maxflow=0; 61 for (int i=s[0];i<=t[0];i++) if (sum[i]>0) add(s[1],i,sum[i]),maxflow+=sum[i]; else add(i,t[1],-sum[i]); 62 if (dinic(1)!=maxflow){puts("-1");return;} 63 maxflow+=dinic(0); 64 printf("%d\\n",maxflow); 65 for (int i=1;i<=id;i++) if (flag[i]) printf("%d\\n",val[(i<<1)+1]+down[i]); 66 } 67 }f; 68 int main(){ 69 while (~scanf("%d%d",&n,&m)){ 70 f.init(),memset(flag,0,sizeof(flag)); 71 for (int i=1;i<=m;i++) scanf("%d",&x),f.add(i+n,f.t[0],x,inf); 72 for (int i=1;i<=n;i++){ 73 scanf("%d%d",&c,&d),f.add(f.s[0],i,0,d); 74 while (c--) scanf("%d%d%d",&a,&x,&y),a++,f.add(i,a+n,x,y),flag[f.id]=1; 75 } 76 f.work(),puts(""); 77 } 78 return 0; 79 }
sgu176 Flow construction
1 #include<cstdio> 2 #include<iostream> 3 #include<cmath> 4 #include<cstring> 5 #include<algorithm> 6 using namespace std; 7 char ch; 8 bool ok; 9 void read(int &x){ 10 for (ok=0,ch=getchar();!isdigit(ch);ch=getchar()) if (ch==‘-‘) ok=1; 11 for (x=0;isdigit(ch);x=x*10+ch-‘0‘,ch=getchar()); 12 if (ok) x=-x; 13 } 14 const int maxn=105; 15 const int maxm=maxn*maxn; 16 const int inf=1061109567; 17 int n,m,a,b,c,d; 18 struct flow{ 19 int s[2],t[2],tot,id,now[maxn],son[maxm],pre[maxm],val[maxm],down[maxm],sum[maxn]; 20 int head,tail,que[maxn],dis[maxn]; 21 bool bo[maxn]; 22 void init(){s[0]=1,t[0]=n,s[1]=0,t[1]=n+1,tot=1,id=0,memset(now,0,sizeof(now)),memset(sum,0,sizeof(sum));} 23 void put(int a,int b,int c){pre[++tot]=now[a],now[a]=tot,son[tot]=b,val[tot]=c;} 24 void add(int a,int b,int c){put(a,b,c),put(b,a,0);} 25 void add(int a,int b,int c,int d){sum[a]-=c,sum[b]+=c,down[++id]=c,add(a,b,d-c);} 26 bool bfs(){ 27 memset(bo,0,sizeof(bo)); 28 memset(dis,0,sizeof(dis)); 29 head=0,tail=1,que[1]=s[1],bo[s[1]]=1; 30 while (head<tail){ 31 int u=que[++head]; 32 for (int p=now[u],v=son[p];p;p=pre[p],v=son[p]) 33 if (val[p]&&!bo[v]) bo[v]=1,dis[v]=dis[u]+1,que[++tail]=v; 34 } 35 return bo[t[1]]; 36 } 37 int dfs(int u,int rest){ 38 if (u==t[1]) return rest; 39 int ans=0; 40 for (int p=now[u],v=son[p];p&&rest;p=pre[p],v=son[p]) 41 if (val[p]&&dis[v]==dis[u]+1){ 42 int d=dfs(v,min(rest,val[p])); 43 val[p]-=d,val[p^1]+=d,ans+=d,rest-=d; 44 } 45 if (!ans) dis[u]=-1; 46 return ans; 47 } 48 int dinic(){ 49 int ans=0; 50 while (bfs()) ans+=dfs(s[1],inf); 51 return ans; 52 } 53 void work(){ 54 int maxflow=0,res=0; 55 for (int i=s[0];i<=t[0];i++) if (sum[i]>0) maxflow+=sum[i],add(s[1],i,sum[i]); else add(i,t[1],-sum[i]); 56 res+=dinic(),add(t[0],s[0],inf),res+=dinic(); 57 if (res!=maxflow){puts("Impossible");return;} 58 printf("%d\\n",val[tot]); 59 for (int i=1;i<=m;i++) printf("%d%c",val[(i<<1)+1]+down[i],i==m?‘\\n‘:‘ ‘); 60 } 61 }f; 62 int main(){ 63 read(n),read(m),f.init(); 64 for (int i=1;i<=m;i++){ 65 read(a),read(b),read(c),read(d); 66 if (d) f.add(a,b,c,c); else f.add(a,b,0,c); 67 } 68 f.work(); 69 return 0; 70 }
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