So, I wanted to create this code to sort strings in a Linkedlist before inserting. I'm not able to find the error in the code but whenever I try to pass the input into the insert function, it says, 'segmentation fault (core dumped)' - something like that.

What I thought was, to sort, I'd use strcmp() to compare strings, and then based on the value, insert. This is the code,

struct node {
  char name[50];
  struct node *next;
};

struct node *insert(struct node *head, char *name) {
  printf("%s NAME",
         name) // To check if the string is correctly passed. Shows above error.
      struct node *toinsert,*temp;
  toinsert = (struct node *)malloc(sizeof(struct node));
  strcpy(toinsert->name, name);
  temp = head;
  while (temp->next != NULL) {
    int a = strcmp(temp->next->name, toinsert->name);
    if (a > 0) {
      break;
    } else {
      temp = temp->next;
    }
  }
  toinsert->next = temp->next;
  temp->next = toinsert;
  return head;
}

int main() {
  struct node *head = NULL;
  char a[48] = "A";
  head = insert(head, a);

  return 0;
}

CodePudding user response：

I fixed the following issues:

1. Missing headers.
2. Syntax error due at printf() due to missing ;.
3. As @HymnsForDisco said you program segfault when it tries to deference a NULL pointer when head is NULL.
4. insert() doesn't do the right thing if node being added should be the new root.
5. (refactor) for-loop is a better fit than while-loop. Either option are correct.
6. (enhancement) added a print function to demonstrate that insert works

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

struct node {
    char name[50];
    struct node *next;
};

struct node *insert(struct node *head, const char *name) {
    struct node *toinsert = malloc(sizeof(struct node));
    strcpy(toinsert->name, name);
    if(!head || strcmp(name, head->name) <= 0) {
        toinsert->next = head;
        return toinsert;
    }
    struct node *temp = head;
    for(; temp->next && strcmp(name, temp->next->name) > 0 ; temp=temp->next);
    toinsert->next = temp->next;
    temp->next = toinsert;
    return head;
}

void print(struct node *head) {
    for(; head; head=head->next) {
        printf("%s\n", head->name);
    }
}

int main() {
    struct node *head = insert(NULL, "B");
    head = insert(head, "A");
    head = insert(head, "C");
    print(head);
}

and the output is:

A
B
C