将一棵树赋值给另一棵树，怎么办？ element D 5形 left_most right_sib r©→形 7777 procedure assign(T1:Tree;Var T2:Tree){ T2:=T1;return null; }将一棵树赋值给另一棵树，怎么办？ procedure assign(T1: Tree; Var T2:Tree){ T2:=T1; return null; } ?