我对C语言编码很陌生（因此我正在做的愚蠢练习）。该代码应该创建一个链表，模拟手里拿着的一副牌。
该代码旨在：（1）取出第一张牌并将其放在桌子上，然后（2）取出新的第一张牌并将其放在手中的牌组的末端。
非常奇怪的是，我的代码在前几次迭代中运行良好，然后突然它开始在屏幕上无休止地打印。 不幸的是，我对 C 的了解不足以理解错误是什么。 我尝试了不同的代码变体，但似乎没有任何效果。
我将非常感谢您的意见。 我已经附上了我的代码和打印输出。 我还突出显示了打印到屏幕的功能。 我猜问题出在函数 add_to_desk（）。
法典：
#include <stdio.h>
#include <stdlib.h>
typedef struct Node {
int data;
struct Node* next;
} *Node_t;
void print_list(Node_t root) {
while (root != NULL) {
printf("%d ", root->data);
root = root->next;
}
printf("n");
}
Node_t first_to_last(Node_t root, Node_t head){
Node_t next_root, last_root;
// get the pointer to the second element
next_root = root->next;
// unlink first element
root->next = NULL;
// rename first element to last
last_root = root;
// reassign root to former second root
root = next_root;
// designate new root as head
head = root;
while (root != NULL) {
if (root->next == NULL) {
root->next = last_root;
break;
}
root = root->next;
}
return head;
}
int delete_first(Node_t *head){
Node_t temp = (*head);
// get data to be returned
int val = (*head)->data;
// reassign head to the second element
*head = (*head)->next;
// unlink former first element
temp->next = NULL;
return val;
}
void add_to_desk(Node_t *desk, Node_t temp){
// check if desk is empty
if ((*desk) == NULL) {
// insert first element
(*desk) = temp;
}
else {
temp->next = (*desk);
(*desk) = temp;
//*desk = temp;
}
}
int main(){
//initialize variables
int val;
int i;
Node_t root, head;
// set size of list of cards
int n = 4;
// allocate memory for temp list
Node_t temp = malloc(sizeof(struct Node));
temp->data = 0;
temp->next = NULL;
// allocate memory for desk cards
Node_t desk = malloc(sizeof(struct Node));
desk->data = 0;
desk->next = NULL;
// allocate memory for list of cards
Node_t list = malloc(sizeof(struct Node) * n);
// initalize list with n cards
for (i=0; i < n; i++) {
list[i].data = i+1;
if (i == n-1) {
list[i].next = NULL;
}
else {
list[i].next = &list[i+1];
}
}
printf("nWe start with these cards in our hand: ");
root = &(list[0]);
print_list(root);
while (1){
while (root != NULL){
val = delete_first(&root);
printf("We have removed the first card of our hand, val = %dn",val);
printf("New list: ");
print_list(root);
printf("Lets add val %d to the stack on the deskn",val);
if (desk->data == 0) {
printf("First time adding to desk stackn");
desk->data = val;
desk->next = NULL;
}
else {
temp->data = val;
printf("Adding val %d to desk stackn",val);
add_to_desk(&desk,temp);
}
printf("New desk stack: ");
print_list(desk);
if (root->next == NULL) {
printf("We are at the last card of our hand, just throw it on the deskn");
temp->data = root->data;
add_to_desk(&desk,temp);
print_list(desk); // <--- HERE'S WHERE PRINTING GOES OUT OF CONTROL
break;
}
else {
head = first_to_last(root, head);
root = head;
printf("We have just moved the first card of our hand to the endn");
printf("New hand order: ");
print_list(root);
}
}
return 1;
}
}
打印输出：
Running…
We start with these cards in our hand: 1 2 3 4
We have removed the first card of our hand, val = 1
New list: 2 3 4
Lets add val 1 to the stack on the desk
First time adding to desk stack
New desk stack: 1
We have just moved the first card of our hand to the end
New hand order: 3 4 2
We have removed the first card of our hand, val = 3
New list: 4 2
Lets add val 3 to the stack on the desk
Adding val 3 to desk stack
New desk stack: 3 1
We have just moved the first card of our hand to the end
New hand order: 2 4
We have removed the first card of our hand, val = 2
New list: 4
Lets add val 2 to the stack on the desk
Adding val 2 to desk stack
New desk stack: 2 2 2 2 2 2 2 2 ...... 2's forever
问题是你只分配一次temp，然后在每次向desk添加卡时重复使用它。
第一次将卡片放在桌子上时没有问题 - 您只需在 malloc 的节点中设置值并分配给变量 desk .
第二次通过，已经分配了 desk，因此您在 malloc 并分配给变量 temp 的节点中设置值，并更新desk使其指向该节点。
第三次是麻烦开始的地方。您将 temp 的值设置为 2，但该temp仍然是您上次使用的对象（它仍然是桌面顶部）。您还会更新其next指针以指向desk - 同样，它仍然是您最初错误定位并分配给temp的同一节点。
换句话说，temp 和 desk 最终指向内存中的同一节点，该节点指向自身。尝试打印它只是意味着一遍又一遍地访问同一张卡，这也意味着您永远不会达到空值，因此您永远不会停止。
else {
temp->next = (*desk);
(*desk) = temp;
//*desk = temp;
}
try to understand this you will find your problem, as you are new so helping you in the
你可以学习的方式...:)它来自Addtodeskfunc还阅读了有关循环链接列表的信息，以获取更多帮助，因为您的代码提供输出，例如指向B和B指向A，因此永远不会发生空指针以结束打印....
这段代码可以正常工作，我刚刚删除了桌子前面的 * 指针。所以它会崩溃。
#include <stdio.h>
#include <stdlib.h>
typedef struct Node {
int data;
struct Node* next;
} *Node_t;
void print_list(Node_t root) {
while (root != NULL) {
printf("%d ", root->data);
root = root->next;
}
printf("n");
}
Node_t first_to_last(Node_t root, Node_t head){
Node_t next_root, last_root;
// get the pointer to the second element
next_root = root->next;
// unlink first element
root->next = NULL;
// rename first element to last
last_root = root;
// reassign root to former second root
root = next_root;
// designate new root as head
head = root;
while (root != NULL) {
if (root->next == NULL) {
root->next = last_root;
break;
}
root = root->next;
}
return head;
}
int delete_first(Node_t *head){
Node_t temp = (*head);
// get data to be returned
int val = (*head)->data;
// reassign head to the second element
*head = (*head)->next;
// unlink former first element
temp->next = NULL;
return val;
}
void add_to_desk(Node_t desk, Node_t temp){
// check if desk is empty
if ((desk) == NULL) {
// insert first element
(desk) = temp;
}
else {
temp->next = (desk);
(desk) = temp;
//*desk = temp;
}
}
int main(){
//initialize variables
int val;
int i;
Node_t root, head;
// set size of list of cards
int n = 4;
// allocate memory for temp list
Node_t temp = malloc(sizeof(struct Node));
temp->data = 0;
temp->next = NULL;
// allocate memory for desk cards
Node_t desk = malloc(sizeof(struct Node));
desk->data = 0;
desk->next = NULL;
// allocate memory for list of cards
Node_t list = malloc(sizeof(struct Node) * n);
// initalize list with n cards
for (i=0; i < n; i++) {
list[i].data = i+1;
if (i == n-1) {
list[i].next = NULL;
}
else {
list[i].next = &list[i+1];
}
}
printf("nWe start with these cards in our hand: ");
root = &(list[0]);
print_list(root);
while (1){
while (root != NULL){
val = delete_first(&root);
printf("We have removed the first card of our hand, val = %dn",val);
printf("New list: ");
print_list(root);
printf("Lets add val %d to the stack on the deskn",val);
if (desk->data == 0) {
printf("First time adding to desk stackn");
desk->data = val;
desk->next = NULL;
}
else {
temp->data = val;
printf("Adding val %d to desk stackn",val);
add_to_desk(desk,temp);
}
printf("New desk stack: ");
print_list(desk);
if (root->next == NULL) {
printf("We are at the last card of our hand, just throw it on the deskn");
temp->data = root->data;
add_to_desk(desk,temp);
print_list(desk); // <--- HERE'S WHERE PRINTING GOES OUT OF CONTROL
break;
}
else {
head = first_to_last(root, head);
root = head;
printf("We have just moved the first card of our hand to the endn");
printf("New hand order: ");
print_list(root);
}
}
return 1;
}
}