简单的dfs。不必考虑时间。瞬秒。

var s,s1,s2:string;    k,n,m:longint;procedure go(k:longint);begin if k=m then begin              write(‘YES‘);              halt;             end; if k>m then exit; go(2*k+1); go(3*k+1);end;begin readln(s); k:=pos(‘,‘,s); s1:=copy(s,1,k-1); delete(s,1,k); s2:=s; val(s1,n); val(s2,m); go(n); write(‘NO‘);end.

noi1_13_41[判断元素是否存在]