[英]Doubly linked list in C
I'm teaching myself C and I'm trying to learn the doubly linked list now. 我正在教自己C,我现在正在努力学习双重链表。 Following the book's tutorial, I have found some problems: 按照本书的教程,我发现了一些问题:
typedef struct _seg {
int bits[256];
struct _seg *next, *prev;
} seg;
EXTERN seg *head;
EXTERN seg *last;
Based on codes like this, I know that to go through the linkedlist from head, I can do something like: 根据这样的代码,我知道要从头开始查看链表,我可以这样做:
seg *p;
p = head;
for ( i = 0; i < k; i++)
p = p->next;
However, how can I reversely go through the linkedlist from the last node(defined as last)? 但是,如何从最后一个节点(定义为last)反向浏览链表?
You could reason symmetrically, and code eg 你可以对称地推理,并编码例如
seg *p = last;
for (int j=0; j < k && p != NULL; j++)
p = p->prev;
I have added the test p != NULL
to avoid an undefined behavior (when the list has fewer than k
elements; on many systems you would get a segmentation violation crash if you omit the test in that case). 我添加了测试p != NULL
以避免未定义的行为 (当列表中的元素少于k
;在许多系统上,如果在这种情况下省略测试,则会导致分段违规崩溃)。
Don't forget to enable all warnings and debugging info when compiling (eg compile with gcc -Wall -g
) and learn how to use the debugger (eg gdb
). 不要忘记在编译时启用所有警告和调试信息(例如使用gcc -Wall -g
编译)并学习如何使用调试器(例如gdb
)。
BTW, C++11 is a different language than C99 or C11 (but with some compatibilities) and offer language support (thru its standard library) for linked lists using std::list . BTW, C ++ 11是一种与C99或C11不同的语言(但具有一些兼容性),并使用std :: list为链表提供语言支持(通过其标准库)。
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