和平委员会 2-sat

按照2-sat的套路直接写就好了...由于要求输出字典序最小的方案数，所以在新图上处理的时候按字典序最小的拓扑序进行染色（不用dfs进行传递）

uses math;var        n,m,l,x,y,tt    :longint;        time,top,size   :longint;        i               :longint;        vis             :array[0..160010] of boolean;        last,la,z       :array[0..160010] of longint;        pre,other,pr,ot :array[0..40010] of longint;        belong,dfn,low  :array[0..160010] of longint;        anti,color,indu :array[0..160010] of longint;        work,heap       :array[0..160010] of longint;procedure swap(var a,b:longint);var        c:longint;begin   c:=a; a:=b; b:=c;end;procedure connect(x,y:longint);begin   inc(l);   pre[l]:=last[x];   last[x]:=l;   other[l]:=y;end; procedure connect2(x,y:longint);begin   inc(l);   pr[l]:=la[x];   la[x]:=l;   ot[l]:=y;end; procedure dfs(x:longint);var        p,q,cur:longint;begin   inc(time);   low[x]:=time;   dfn[x]:=time;   inc(top);   z[top]:=x;   vis[x]:=true;   //   q:=last[x];   while q<>0 do   begin      p:=other[q];      if (dfn[p]=0) then      begin         dfs(p);         low[x]:=min(low[x],low[p]);      end else      if vis[p] then low[x]:=min(low[x],dfn[p]);      q:=pre[q];   end;   //   if low[x]=dfn[x] then   begin      cur:=-1; inc(tt);      while cur<>x do      begin         cur:=z[top];         dec(top);         vis[cur]:=false;         belong[cur]:=tt;      end;   end;end;procedure rebuild;var        i,p,q:longint;begin   l:=0;   for i:=1 to n<<1 do   begin      q:=last[i];      while q<>0 do      begin         p:=other[q];         if belong[i]<>belong[p] then         begin            connect2(belong[p],belong[i]);            inc(indu[belong[i]]);         end;         q:=pre[q];      end;   end;end;procedure heap_down(i:longint);var        t:longint;begin   while (i<<1)<=size do   begin      if heap[i]<heap[i<<1] then t:=i else t:=i<<1;      if (i<<1)+1<=size then        if heap[t]>heap[(i<<1)+1] then t:=(i<<1)+1;      if i<>t then      begin         swap(heap[i],heap[t]);         i:=t;      end else exit;   end;end;procedure heap_up(i:longint);begin   if i=1 then exit;   while i>1 do   begin      if heap[i]<heap[i>>1] then      begin         swap(heap[i],heap[i>>1]);         i:=i>>1;      end else exit;   end;end;procedure insert(x:longint);begin   inc(size);   heap[size]:=x;   heap_up(size);end;procedure topsort_col;var        p,q:longint;begin   while size<>0 do   begin      x:=heap[1];      heap[1]:=heap[size]; dec(size); heap_down(1);      if color[x]=0 then      begin         color[x]:=1;         color[anti[x]]:=2;      end;      q:=la[x];      while q<>0 do      begin         p:=ot[q];         dec(indu[p]);         if indu[p]=0 then insert(p);         q:=pr[q];      end;   end;end;begin   assign(input,'spo.in');reset(input);   assign(output,'spo.out');rewrite(output);   read(n,m);   for i:=1 to m do   begin      read(x,y);      if (y and 1=1) then connect(x,y+1) else connect(x,y-1);      if (x and 1=1) then connect(y,x+1) else connect(y,x-1);   end;   for i:=1 to n<<1 do if dfn[i]=0 then dfs(i);   for i:=1 to n do     if (belong[i<<1]=belong[(i<<1)-1]) then     begin        writeln('NIE'); close(input); close(output); exit;     end;   rebuild;   for i:=1 to n do   begin      anti[belong[i<<1]]:=belong[(i<<1)-1];      anti[belong[(i<<1)-1]]:=belong[i<<1];   end;   for i:=1 to tt do if indu[i]=0 then insert(i);   topsort_col;   //   for i:=1 to n<<1 do    if color[belong[i]]=1 then writeln(i);   close(input); close(output);end.

——by Eirlys