在C段错误中附加链接列表

Question

I am having some trouble adding integers to the end of my linked list. I am very new to C and had part of my program working properly (the push function). I want to return a pointer to a struct node, and I am not quite sure where I am going wrong in my append function.

~Thanks.

 enter code here


 //node.h

 #ifndef NODE_H
 #define NODE_H

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

 int length(struct node *);
 struct node* push(struct node *, int);     //adds integer to front of list.
 struct node* append(struct node *, int);   //adds integer to back of list.
 void print(struct node *, int);

 #endif


 //node.c

 #include "./node.h"
 #include<stdlib.h>
 #include<stdio.h>

 int length(struct node *current){
    if(current->next != NULL)
    return 1 + length(current->next);
 else
  return 1;
 }

 struct node* push(struct node *head, int num){

    struct node *temp = malloc(sizeof(struct node));
    temp->val = num;
    temp->next = head;
    head = temp;
    temp = NULL;
    return head;
    }

    struct node* append(struct node *current, int num){

       if(current != NULL){
       append(current->next, num);
       }

       else{
         struct node* temp = malloc(sizeof(struct node));
         temp->val = num;
       temp->next = NULL;
       current = temp;
       return current;

       }
       } 



void print(struct node* head, int size){

   printf("The list is %i", size);
   printf(" long \n");
   struct node* temp;
   temp = head;
   while(temp != NULL){
   printf("%d", temp->val);
   printf(" ");
   temp = temp->next;
   }
   printf(" \n");
   }


  //Main

  #include "./node.h"
  #include<stdlib.h>
  #include<stdio.h>

  int main(){

    char ans[2];
    int num;
    struct node* head = NULL;

    do{
     printf("Enter a integer for linked list: ");
     scanf("%d", &num);

     head = append(head, num);
     printf("Add another integer to linked list? (y or n) ");
     scanf("%1s", ans);
     }while(*ans == 'y');

     print(head, length(head));

     return 0;
     }

Answer 1

I think what is missing is that the recursive part of the function needs to set current->next. This has the effect of setting every node's next pointer to what it was until you get to the end of the list, when it is set to the newly malloced node.

struct node* append(struct node *current, int num){

       if(current != NULL){
         current->next = append(current->next, num);
         return current;
       }
       else {
         struct node* temp = malloc(sizeof(struct node));
         if (temp == NULL) abort();
         temp->val = num;
         temp->next = NULL;
         return temp;
       }
}