bzoj2791

每个顶点有且仅有一条出边是什么意思呢

类似一棵树，树上的边都是由儿子指向父亲的，并且这个东西带着一个环

也就是一个个有向环套有向树……

这题还是比较简单的，把环作为根然后类似lca做即可，注意细节的panding

 type node=record
        po,next:longint;
      end;

 var e:array[..] of node;
     s,p,w,c,be,d,q:array[..] of longint;
     v:array[..] of boolean;
     anc:array[..,..] of longint;
     t,f,r,n,m,len,i,x,y,a,b:longint;

 function max(a,b:longint):longint;
   begin
     if a>b then exit(a) else exit(b);
   end;

 function min(a,b:longint):longint;
   begin
     if a>b then exit(b) else exit(a);
   end;

 procedure swap(var a,b:longint);
   var c:longint;
   begin
     c:=a;
     a:=b;
     b:=c;
   end;

 procedure add(x,y:longint);
   begin
     inc(len);
     e[len].po:=y;
     e[len].next:=p[x];
     p[x]:=len;
   end;

 procedure bfs;
   var x,i,y:longint;
   begin
     f:=;
     while f<=r do
     begin
       x:=q[f];
       for i:= to  do
       begin
         y:=anc[x,i-];
         if y<> then anc[x,i]:=anc[y,i-] else break;
       end;
       i:=p[x];
       while i<> do
       begin
         y:=e[i].po;
         if not v[y] then
         begin
           d[y]:=d[x]+;
           anc[y,]:=x;
           be[y]:=t;
           inc(r);
           q[r]:=y;
           v[y]:=true;
         end;
         i:=e[i].next;
       end;
       inc(f);
     end;
   end;

 procedure lca(x,y:longint);
   var i,num,a1,b1,a2,b2:longint;
   begin
     a:=; b:=;
     if d[x]>d[y] then
       for i:= downto  do
         if d[x]- shl i>=d[y] then
         begin
           x:=anc[x,i];
           a:=a+ shl i;
         end;

     if d[y]>d[x] then
       for i:= downto  do
         if d[y]- shl i>=d[x] then
         begin
           y:=anc[y,i];
           b:=b+ shl i;
         end;

     if x=y then exit;
     for i:= downto  do
       if (anc[x,i]<>anc[y,i]) then
       begin
         x:=anc[x,i]; a:=a+ shl i;
         y:=anc[y,i]; b:=b+ shl i;
       end;

     if (anc[x,]=anc[y,]) and (anc[x,]<>) then
     begin
       inc(a); inc(b);
       exit;
     end;
     num:=s[be[x]];
     if c[x]>c[y] then a1:=a+num-c[x]+c[y] else a1:=a+c[y]-c[x];
     b1:=b;
     a2:=a;
     if c[x]<c[y] then b2:=b+num-c[y]+c[x] else b2:=b+c[x]-c[y];
     if max(a1,b1)=max(a2,b2) then
     begin
       if (min(a1,b1)>min(a2,b2)) or (min(a1,b1)=min(a2,b2)) and (a1<b1) then
       begin
         a:=a2;
         b:=b2;
       end
       else begin
         a:=a1;
         b:=b1;
       end;
     end
     else if max(a1,b1)>max(a2,b2) then
     begin
       a:=a2;
       b:=b2;
     end
     else begin
       a:=a1;
       b:=b1;
     end;
   end;

 begin
   readln(n,m);
   for i:= to n do
   begin
     read(w[i]);
     add(w[i],i);
   end;

   for i:= to n do
     if be[i]= then
     begin
       inc(t);
       be[i]:=t;
       x:=i;
       while true do
       begin
         x:=w[x];
         if be[x]=t then break;
         be[x]:=t;
       end;
       y:=x;
       r:=;
       repeat
         inc(s[t]);
         c[y]:=s[t];
         inc(r);
         q[r]:=y;
         v[y]:=true;
         y:=w[y];
       until y=x;
       bfs;
     end;

   for i:= to m do
   begin
     readln(x,y);
     if be[x]<>be[y] then
     begin
       writeln('-1 -1');
       continue;
     end;
     lca(x,y);
     writeln(a,' ',b);
   end;
 end.