Question

how do i return and array of string (2d array) from a single linkedlist in c?

for example i have a linkedlist that contains

cat->dog->dish

how do i return them to main as an array

(cat,dog,dish)

Answer 1

Remember in C Language you can directly return the array from a function . If you need to return the array of values then you need to use pointers and double pointers.

CODE:

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

//template for node
struct node
{
char *data; //char pointer to store string
struct node *next; //next pointer to hold reference of next node
};
char** getArrayFromLinkedlist(struct node *head) //method which returns array when linked list head is given
{
struct node * temp=head; //assigning head to temp;
int length=0;
while(temp!=NULL) //finding length of linked list;
{
length++; //incrementing length
temp=temp->next; //moving to next node
}
char ** array = malloc(length * sizeof(char*)); //declaring dynamic memory for out double pointer to store srray of strings
  
temp=head;
int i=0;
while(temp!=NULL) //iteratin over linked list
{
array[i]=malloc(20 * sizeof(char)); //allocating memory for out string(here max length is 20)
array[i]=temp->data; //setting linked list data to array
i=i+1; //incrementing array index
temp=temp->next; //moving to next node;
}
array[i]=NULL; //setting last element of array to NULL
return array; //returning array
  
  
}

int main()
{
struct node *head=NULL; //head node of linked list
//allocating memory
head = (struct node*)malloc(sizeof(struct node));
struct node *newnode1=(struct node*)malloc(sizeof(struct node));
struct node *newnode2=(struct node*)malloc(sizeof(struct node));

//Setting temporary data
char *word1="cat";
head->data = malloc(strlen(word1) + 1); //allocating memory
head->data=word1;
head->next=newnode1;
char * word2="dog";
newnode1->data = malloc(strlen(word2) + 1); newnode1->next=newnode2;
newnode1->data=word2;
char *word3="dish";
newnode2->data = malloc(strlen(word3) + 1); newnode2->next=NULL;
newnode2->data=word3;
char** mystr=getArrayFromLinkedlist(head); //callin our method which return double pointer
while(*mystr) //iteratig over array of strings
{
printf("%s ",*mystr);
mystr++;
}
return 0;
}

OUTPUT:

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