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.