LCA倍增算法的错误与模板

先上我原来的错误的代码

type
  node=^link;
  link=record
    num:int64;
    next:node;
  end;

var
 fa:array[..,..] of int64;
 dep:array[..] of int64;
   nd:array[..] of node;
  b:array[..] of boolean;
  dl:array[..] of int64;
 n,m,maxdep,ans,t1,t2:int64;
 i:longint;

 procedure maketree;
 var
  t1,t2,head,tail:int64;
  i,j:longint;
  p:node;
   begin

     for i:= to n do
       b[i]:=false;

     for i:= to n- do
       begin
         read(t1,t2);

         new(p);
         p^.num:=t2;p^.next:=nd[t1];nd[t1]:=p;
         new(p);
         p^.num:=t1;p^.next:=nd[t2];nd[t2]:=p;
       end;

      new(p);
      head:=;tail:=;dl[head]:=;b[]:=true;
       while head<=tail do
         begin
           p:=nd[dl[head]];

           while p<>nil do
             begin
               if b[p^.num]=false then
                 begin
                   inc(tail);
                   dl[tail]:=p^.num;
                   fa[p^.num,]:=dl[head];
                   dep[p^.num]:=dep[dl[head]]+;
                   b[p^.num]:=true;
                   if dep[p^.num]>maxdep then maxdep:=dep[p^.num];
                 end;
               p:=p^.next;
             end;

           inc(head);
         end;

      for j:= to trunc(ln(maxdep)/ln())+ do
        for i:= to n do
          if dep[i]>=<<j then
            fa[i,j]:=fa[fa[i,j-],j-];
   end;

  procedure lca(a,b:longint);
  var
   i,t:longint;
    begin
      if dep[a]>dep[b] then
        begin
          t:=a;
          a:=b;
          b:=t;
        end;

      if dep[a]<>dep[b] then
        for i:=trunc(ln(dep[b]-dep[a])/ln()) downto  do
          if dep[b]-<<i>=dep[a] then
            begin
               b:=fa[b,i];
               ans:=ans+<<i;
            end;

     if a<>b then
      for i:=trunc(ln(dep[a])/ln()) downto  do
        if fa[a,i]<>fa[b,i] then
          begin
            a:=fa[a,i];
            b:=fa[b,i];
            ans:=ans+<<(i+);
          end;

      if a<>b then inc(ans,);
    end;

  begin

    readln(n);

    if n= then
      begin
        writeln();
        halt;
      end;

    maketree;

    readln(m);

    read(t1);
    for i:= to m do
      begin
        read(t2);

        lca(t1,t2);
        t1:=t2;
      end;

    writeln(ans);

  end.

这个写法WA了一个点，答案比标准答案大。

最后发现可能是ln出现了误差，导致结果偏小，使两点无法移到同层。在后面的移动中无论怎样都无法移到同点，使答案比原来大二

改正后的模板

type
  node=^link;
  link=record
    num:int64;
    next:node;
  end;

var
 fa:array[..,..] of int64;
 dep:array[..] of int64;
   nd:array[..] of node;
  b:array[..] of boolean;
  dl:array[..] of int64;
  n,m,maxdep,ans,t1,t2:int64;
  i:longint;

 procedure maketree;
 var
  t1,t2,head,tail:int64;
  i,j:longint;
  p:node;
   begin

     for i:= to n do
       b[i]:=false;

     for i:= to n- do
       begin
         read(t1,t2);

         new(p);
         p^.num:=t2;p^.next:=nd[t1];nd[t1]:=p;
         new(p);
         p^.num:=t1;p^.next:=nd[t2];nd[t2]:=p;
       end;

      new(p);
      head:=;tail:=;dl[head]:=;b[]:=true;
       while head<=tail do
         begin
           p:=nd[dl[head]];

           while p<>nil do
             begin
               if b[p^.num]=false then
                 begin
                   inc(tail);
                   dl[tail]:=p^.num;
                   fa[p^.num,]:=dl[head];
                   dep[p^.num]:=dep[dl[head]]+;
                   b[p^.num]:=true;
                   if dep[p^.num]>maxdep then maxdep:=dep[p^.num];
                 end;
               p:=p^.next;
             end;

           inc(head);
         end;

      for j:= to trunc(ln(maxdep)/ln())+ do
        for i:= to n do
          if dep[i]>=<<j then
            fa[i,j]:=fa[fa[i,j-],j-];
   end;

  procedure lca(a,b:longint);
  var
   i,t:longint;
    begin
      if dep[a]>dep[b] then
        begin
          t:=a;
          a:=b;
          b:=t;
        end;

      if dep[a]<>dep[b] then
        for i:=trunc(ln(dep[b]-dep[a])/ln())+ downto  do
          if dep[b]-<<i>=dep[a] then
            begin
               b:=fa[b,i];
               ans:=ans+<<i;
            end;

     if a<>b then
      for i:=trunc(ln(dep[a])/ln())+ downto  do
        if fa[a,i]<>fa[b,i] then
          begin
            a:=fa[a,i];
            b:=fa[b,i];
            ans:=ans+<<(i+);
          end;

      if a<>b then inc(ans,);
    end;

  begin

    readln(n);

    if n= then
      begin
        writeln();
        halt;
      end;

    maketree;

    readln(m);

    read(t1);
    for i:= to m do
      begin
        read(t2);

        lca(t1,t2);
        t1:=t2;
      end;

    writeln(ans);

  end.