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

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


// Delete the first instance of a duplicate in the list 
struct node *delete_duplicate(struct node *head) {
    // Edge: empty list
    if (head == NULL || head->next == NULL) {
        return head;
    }

    struct node *current = head;

    while (current != NULL) {
        // 3 4 4 5
        // current = 3
        struct node *other = current->next;
        // o[ther = 4
        struct node *previous = current;
        while (other != NULL) {

            if (other->data == current->data) {
                struct node *temp = other->next;
                previous->next = temp;
                free(other);
                return head;
            }
            previous = other;
            other = other->next;
        }
        current = current->next;
    }



    return NULL;
}


// DO NOT CHANGE CODE BELOW

struct node *strings_to_list(int len, char *strings[]);
void print_list(struct node *head);


int main(int argc, char *argv[]) {
    // create linked list from command line arguments
    struct node *head = NULL;
    if (argc > 1) {
        // list has elements
        head = strings_to_list(argc - 1, &argv[1]);
    }

    struct node *new_head = delete_duplicate(head);
    print_list(new_head);

    return 0;
}


// create linked list from array of strings
struct node *strings_to_list(int len, char *strings[]) {
    struct node *head = NULL;
    int i = len - 1;
    while (i >= 0) {
        struct node *n = malloc(sizeof (struct node));
        assert(n != NULL);
        n->next = head;
        n->data = atoi(strings[i]);
        head = n;
        i -= 1;
    }   
    return head;
}

// print linked list
void print_list(struct node *head) {
    printf("[");    
    struct node *n = head;
    while (n != NULL) {
        // If you're getting an error here,
        // you have returned an invalid list
        printf("%d", n->data);
        if (n->next != NULL) {
            printf(", ");
        }
        n = n->next;
    }
    printf("]\n");
}