UVA10735 混合图欧拉回路
from CAH，here
讲的比lrj还要详细，
个人的傻逼错误：
需要注意的是，网络流里是有反向边的，dinic跑完之后反向边不要添加到新图里面了
#includeif (vis[e.to]||e.cap<=e.flow)continue;
vis[e.to]=1;
d[e.to]=d[x]+1;
Q.push(e.to);
}
}
return vis[t];
}
inline int DFS(const int& x,int a){
if (x==t||a==0){return a;}
int flow = 0, f;
for (int& i=cur[x];iif (d[x]+1!=d[e.to])continue;
if ((f=DFS(e.to,min(a,e.cap-e.flow)))<=0)continue;
e.flow += f;
edges[G[x][i]^1].flow-=f;//ϲߍ
flow+=f; a-=f;
if (!a) break;
}
return flow;
}
inline int maxFlow(){return maxFlow(s,t);}
inline int maxFlow(int s, int t){
int flow = 0;
for (;BFS();){
memset(cur,0,sizeof(cur));
flow += DFS(s,INF) ;
}
return flow;
}
inline void buildEuler(int n){
for (int i=1;i<=n;i++){
for (int j=0;jif (e.to==s||e.to==t) continue ;
if (!e.cap)continue;
if (e.flow==e.cap)gg.AddEdge(e.to,e.from);
else gg.AddEdge(e.from, e.to);
}
}
}
} g ;
int d[N];//degree = out - in
bool work(int n){
int flow = 0;
for (int i=1;i<=n;i++){
if (d[1]&1)return 0;
if (d[i]>0){
g.AddEdge(g.s,i,d[i]>>1);
flow += d[i]>>1;
}else if (d[i]<0)
g.AddEdge(i,g.t,-(d[i]>>1));
}
if (flow != g.maxFlow()) return 0;
return 1;
}
int main(){
//freopen("in.txt","r",stdin);
int T,x,y,n,m;
scanf("%d",&T);
for (char ch;T--;){
scanf("%d%d",&n,&m);
g.Init(n,0,n+1);
gg.Init(n);
memset(d,0,sizeof(d));
for (int i=1;i<=m;i++){
scanf("%d%d %c\n",&x,&y,&ch);
if (ch=='D') gg.AddEdge(x,y);
else g.AddEdge(x,y,1);
d[x]++;d[y]--;//Degree
}
if (!work(n))puts("No euler circuit exist");
else {
g.buildEuler(n);
gg.getEulerCircle();
}
if (T)puts("");
}
return 0;
}
前行星的dinic板
struct Dinic
{
struct Edge{
int from,to,cap,flow,nxt;
Edge(){}
Edge(int u,int v,int c,int f,int n):
from(u),to(v),cap(c),flow(f),nxt(n){}
}edges[N];
int n, s, t, E, head[N];
bool vis[N]; //use when bfs
int d[N],cur[N];//dist,now edge,use in dfs
inline void AddEdge(int f,int t,int c){
edges[++E] = Edge(f,t,c,0,head[f]);
head[f] = E;
edges[++E] = Edge(t,f,0,0,head[t]);
head[t] = E;
}
inline void Init(int n,int s,int t){
this -> n = n ; E = -1;
this -> s = s ; head[s] = -1;
this -> t = t ; head[t] = -1;
for (int i=0;i<=n;i++) head[i] = -1;
}
inline bool BFS(){
memset(vis,0,sizeof(vis));
queue<int >Q;
d[s] = 0; vis[s] = 1;
for (Q.push(s);!Q.empty();){
int x = Q.front(); Q.pop();
for (int nxt,i = head[x];i!=-1;i = nxt){
Edge &e = edges[i]; nxt = e.nxt;
if (vis[e.to]||e.cap<=e.flow)continue;
vis[e.to]=1;
d[e.to]=d[x]+1;
Q.push(e.to);
}
}
return vis[t];
}
inline int DFS(const int& x,int a){
if (x==t||a==0){return a;}
int flow = 0, f, nxt;
for (int& i=cur[x];i!=-1;i=nxt){
Edge& e = edges[i]; nxt = e.nxt;
if (d[x]+1!=d[e.to])continue;
if ((f=DFS(e.to,min(a,e.cap-e.flow)))<=0)continue;
e.flow += f;
edges[i^1].flow-=f;//反向边
flow+=f; a-=f;
if (!a) break;
}
return flow;
}
inline int maxFlow(){return maxFlow(s,t);}
inline int maxFlow(int s, int t){
int flow = 0;
for (;BFS();){
for (int i=0;i<=n;i++)cur[i]=head[i];
flow += DFS(s,INF) ;
}
return flow;
}
inline void buildEuler(int n){
for (int i=1;i<=n;i++){
for (int nxt,j=head[i];j!=-1;j=nxt){
Edge &e = edges[j]; nxt = e.nxt;
if (e.to==s||e.to==t) continue ;
if (!e.cap)continue;
if (e.flow==e.cap)gg.AddEdge(e.to,e.from);
else gg.AddEdge(e.from, e.to);
}
}
}
} g ;