判断带头结点的双向循环链表L是否对称相等的算法如下所示请在划线处填上正确的语句
FUNCTION equal(l:pointer) :boolean;
VAR pq:pointer; result: Boolean;
BEGIN result =true ; p:= l^link; q:=l^pre ;
WHILE (p<>q) AND (()_______)DO
IF p^data=q^data THEN BEGIN ()______; ()______; END
ELSE result=false ;
return(result);
END;【华南师范大学 年 五 ( 分)】
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