c++ - 关于C语言链表的while循环

Question

while(num!=q->num&&q!=NULL){
q=q->next;
}//q为一个链表

这样写有什么问题吗？经过我不断的debug，基本把错误缩小到这句上，程序也能运行，但是输入一个数赋值给num后，程序会报错。具体表现为程序停止工作。

已找到原因，吧q!=NULL和num!=q->num调一下位置就行了。

Answer 1

&& operator first evaluates the expression on the left. If it is false, it returns false directly. If it is true, it evaluates the expression on the right.

Answer 2

Isn’t this a problem of short-circuit evaluation?

As operand expressions of "&&" and "||" operators, when these expressions are evaluated, as long as the final result can be determined to be true or false, the evaluation process will terminate. , this is called short-circuit evaluation. This is an important property of these two operators.

You should first determine whether q is null. According to the rules of short-circuit evaluation, the statement num!=q->num will be executed only when q is not null. In this way, the problem of null pointer can be avoided.