数据结构尾插法 求指点 完全不会

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


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

struct node* tailinsert();
void destroy(struct node* head);
void traverse(struct node* head);


void traverse(struct node* head)
{
    if (head == NULL)
    {
        return;
    }
    else
    {
        struct node* tmp = head->next;

        while (tmp != NULL)
        {
            if (tmp->next != NULL)
            {
                printf("%c ", tmp->data);
            }
            else
            {
                printf("%c", tmp->data);
            }
            tmp = tmp->next;
        }
        printf("\n");
    }
}


void destroy(struct node* head)
{
    if (head == NULL)
    {
        return;
    }
    else
    {
        struct node* P;
        struct node* tmp;
        P = head->next;
        head->next = NULL;
        while (P != NULL)
        {
            tmp = P->next;
            free(P);
            P = tmp;
        }
        free(head);
        head = NULL;
    }
}

struct node* tailinsert()
{
    char arr[5];
    int i = 0;
    scanf("%s",arr);
    struct node* begin = (struct node*)malloc(sizeof(struct node));
    if (begin == NULL)
    {
        return;
    }
    struct node* end = begin;
    end->next = NULL;
    for (i = 0; i < 5; i++)
    {
        struct node* new = (struct node*)malloc(sizeof(struct node));
        if (new == NULL)
        {
            return;
        }
        new->data = arr[i];
        new->next = NULL;
        end->next = new;
        end = new;
    }
    return begin;
}

void main()
{
    struct node* head = NULL;
    head = tailinsert();
    traverse(head);
    destroy(head);
}

如图：不明白的追问