为什么我的链表程序会无限地打印出我输入的那个“第一个数字”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 number\n");
        scanf("%d", &x);
        Insert(x); 
        Print();
    }

Example of the wrong output that I got from my compiler:

How many numbers?

My input: 2

Enter the number:

My input: 1

List is: 1111111111111111111111111111111111111111111111111111111111111111111111111111111111111 and it goes on & on & on

I didn't even have the chance to enter the 2nd number, since I put 2 numbers as the amount of numbers.

Answer 1

I refactored the code and it's worked.

The infinite loop was due to the first node pointing to the head and the head pointing to the first node.

temp->next = head;
head = temp;

So when you call Print() the while(temp != NULL) condition never fails.

struct Node{
    int data;
    struct Node* next; 
};

struct Node* head;

void Insert(int x){ 
    struct Node* temp = malloc(sizeof(struct Node));
    if (temp==NULL) { printf("No available space on heap\n"); 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("\n");
}
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 number\n");
        scanf("%d", &x);
        Insert(x); 
       
    }
  Print();  
  destroy_mem(head);
}