c语言 - 为什么我的链表程序无限地打印出我输入的那个"first number"的循环？

Question

#include<stdlib.h>
#include<stdio.h>
struct Node{
int data;
struct Node* next; 
};
struct Node* head;
void Insert(int x){ 
struct Node* temp = (struct Node*)malloc(sizeof(struct Node));
temp->data  = x; 
temp->next = head;
head = temp;
if(head != NULL)
temp->next = head;
head = temp;
}
void Print(){
struct Node* temp = head; 
printf("List is: ");
while(temp != NULL){
printf("%d", temp->data);
temp = temp->next;
}
printf("n");
}
int main(){
head = NULL; //empty list
printf("How many numbers?n");
int n, i;
scanf("%d", &n);
for(int i=0; i < n; i++){
printf("Enter the numbern");
scanf("%d", &x);
Insert(x); 
Print();
}

我从编译器得到的错误输出示例：

有多少个数字？

我的输入：2

输入数字：

我的输入：1

列表是：1111111111111111111；在&在上

我甚至没有机会输入第二个数字，因为我把2个数字作为数字的数量。

Answer 1

我重构了代码，它成功了。

无限循环是由于第一个节点指向头部，头部指向第一个节点。

temp->next = head;
head = temp;

因此，当您调用Print()时，while(temp != NULL)条件永远不会失败。

#include <stdio.h>
#include<stdlib.h>
struct Node{
int data;
struct Node* next; 
};
struct Node* head;
void push_front(int x) { 
struct Node *current = malloc( sizeof( struct Node ) ); 
if (current==NULL) { printf("No available space on heapn"); exit(1); }
current->data = x; 
current->next = head; 
head = current; 
} 
void append(int x){ 
struct Node* temp = malloc(sizeof(struct Node));
if (temp==NULL) { printf("No available space on heapn"); exit(1); }
temp->data  = x; 
temp->next = NULL;
//check if we have to insert at begining(initial node) or empty list
if (head==NULL){
head=temp;
return ;
}
//traverse till the last node to insert new node
//should not modify the head
struct Node *t=head;
while(t->next != NULL) t=t->next;
t->next= temp;
}
void Print(){
struct Node* temp = head; 
printf("List is: ");
while(temp != NULL){
printf("%d->", temp->data);
temp = temp->next;
}
printf("nulln");
}
void destroy_mem(struct Node *head)
{//we need destroy the used memory on heap for further use
struct Node *curr = NULL;
while ((curr = head) != NULL)
{                      // set curr to head, stop if list empty.
head = head->next; // moving head to next element.
free(curr);        // delete saved pointer.
}
head = NULL;
}
int main(){
head = NULL; //empty list
printf("How many numbers?n");
int n, i,x;
scanf("%d", &n);
for(int i=0; i < n; i++){
printf("Enter the numbern");
scanf("%d", &x);
push_front(x); 

}
Print();  
destroy_mem(head);
}