我无法得到在给定节点的开头、结尾和后面插入节点的输出。我不确定main（）中是否遗漏了什么。我无法指出程序中的逻辑错误。

#include<stdio.h>
#include<stdlib.h>

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

//Inserts at the begining
void push(struct node **head, int x){
    struct node *newnode = (struct node *)malloc(sizeof(struct node));
    newnode->data = x; 
    *head = newnode;
    newnode->next = (*head);
    *head = newnode;
}

//Insert at the last 
void append(struct node **head, int x){
    struct node *temp;
    struct node* newnode = (struct node*)malloc(sizeof(struct node));
    newnode->data = x;
    newnode->next = 0;
    if(*head == 0){
        *head = newnode;
    }
    temp = *head;
   while(temp->next != 0){
        temp = temp->next;
   }
   temp->next = newnode;
}

//inserting at a given node 
void insertAfter(struct node* temp, int x){
    if(temp == NULL){
        printf("previous node cannot be NULL");
    }
    struct node* newnode = (struct node*)malloc(sizeof(struct node));
    newnode->data = x;
    newnode->next = temp->next;
    temp->next = newnode;   
}

void printList(struct node *temp){
    while(temp->next != NULL){
        printf("%d",temp->data);
    }
    temp = temp->next;
}

int main(){
    struct node *head = NULL;
    append(&head,6);
    push(&head, 7);
    push(&head, 1);
    append(&head, 4);
    insertAfter(head->next, 8);
    printf("Created linked list is:\n"); 
    printList(head);
    return 0;
}

`
输出为1 7 8 6 4
但我没有得到输出，也没有错误