prufer码水题
（n-2)！/[(d1-1)!*(d2-1)!*…*(dn-1)!]
1 var c:array[0..200] of longint; 2 x,n,i,j,s:longint; 3 ans:int64; 4 5 begin 6 readln(n); 7 if n=1 then 8 begin 9 readln(x); 10 if x=1 then writeln(0) 11 else writeln(1); 12 halt; 13 end; 14 for i:=1 to n do 15 begin 16 read(x); 17 if (x<1) or (x>n) then 18 begin 19 writeln(0); 20 halt; 21 end; 22 for j:=2 to x-1 do 23 inc(c[j]); 24 s:=s+x-1; 25 end; 26 if s<>n-2 then 27 begin 28 writeln(0); 29 halt; 30 end; 31 ans:=1; 32 for i:=2 to n-2 do 33 begin 34 ans:=ans*int64(i); 35 for j:=2 to n do 36 begin 37 while (c[j]>0) and (ans mod j=0) do 38 begin 39 dec(c[j]); 40 ans:=ans div j; 41 end; 42 end; 43 end; 44 writeln(ans); 45 end.
