强连通分量tarjan缩点

cnt:=1
res:=0
for i=1 to 总点数
   if book[i]=0
      TARJAN(i) endif
endfor
print res

book[u]:=1
low[u]:=dfn[u]:=cnt
cnt:=cnt+1
for i:=0 to (连接u的点数-1)
   v:=连接u的第(i+1)个点
   if book[v]=0
      TARJAN(v) endif
   if book[v]=1
      low[u]=MIN(low[u],low[v]) endif
endfor
if dfn[u]=low[u]
   res:=res+1