/*
 * You will write a function list_add() to append an integer to the end
 * of a linked list. You will also write a function called list_find() that
 * will return the list node containing the integer value or NULL if the
 * value is not in the list.
 */

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

struct lnode {
    int value;
    struct lnode *next;
};

struct list {
    struct lnode *head;
    struct lnode *tail;
};


/* Append the value to the end of the linked list */
void list_add(lst, value)
    struct list *lst;
    int value;
{
    /*1. Allocate the new node in the heap. */
    struct lnode* newNode;
    newNode = malloc(sizeof(struct lnode));
    /*2. Set its value to value argument */
    newNode->value = value;
    /*3. Make the next pointer point to NULL, it's at the end of our list */
    newNode->next = NULL;
    /* Check if it's the first node in list */
    if (lst->head == NULL) {
        lst->head = newNode;
        lst->tail = newNode;
    /* If it's not, add it to the end of the list */
    } else {
        lst->tail->next = newNode;
        lst->tail = newNode;
    }
}
/* Search for the user-provided value in the given user-provided linked list */
struct lnode* list_find(lst, value)
    struct list *lst;
    int value;
{
    /* Create a pointer to a current node */
    struct lnode *cur;

    /* Iterate through the list searching for user-provided value */
    for (cur = lst->head; cur != NULL; cur = cur->next) {
        /* If we find the value, return the lnode */
        if (cur->value == value) {
            return cur;
        }
    }
    return NULL;
}

void list_remove(lst, value)
    struct list *lst;
    int value;
{
    /* Remove the value from the linked list. */

    /* Search the linked list until you find the value */
    /* Need to keep track of the previous node so we can update the links */
    struct lnode* cur;
    struct lnode* prev;

    /* Initialize prev */
    prev = NULL;

    for (cur = lst->head; cur != NULL; cur = cur->next) {
        /* Value found */
        if (cur->value == value) {
            /* Value to be removed is at front of list */
            if (prev == NULL) {
                lst->head = cur->next;
            } else {
                prev->next = cur->next;
            }
            free(cur);
            /* deleted the value, end the loop */
            break;
        } else {
        /* Value not found */
        prev = cur;
        }
    }
}

void list_dump(lst)
    struct list *lst;
{
    struct lnode *cur;
    printf("\nDump:\n");
    for(cur=lst->head; cur != NULL; cur=cur->next) {
        printf(" %d\n", cur->value);
    }
};

int main()
{
    void list_add();
    void list_dump();
    void list_remove();
    struct lnode * list_find();

    struct list mylist;
    struct lnode * mynode;

    mylist.head = NULL;
    mylist.tail = NULL;

    list_add(&mylist, 10);
    list_add(&mylist, 20);
    list_add(&mylist, 30);
    list_dump(&mylist);

    list_remove(&mylist, 42);

    list_remove(&mylist, 10);
    list_dump(&mylist);

    list_remove(&mylist, 30);
    list_dump(&mylist);

    list_add(&mylist, 40);
    list_dump(&mylist);

}