Linked List

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

typedef struct node {
    int value;
    struct node *next;
} node;

void print_list(node *head) {
    while (head != NULL) {
        printf("%d -> ", head->value);
        head = head->next;
    }
    printf("NULL\n");
}

node *insert_head(node *head, int val) {
    node *new = malloc(sizeof(node));
    new->next = head;
    new->value = val;
    return new;
}

void in_order_insert(node **head, int val) {
    node *new = malloc(sizeof(node));
    node **curr = head;
    node **prev = NULL;

    while (*curr && val > (*curr)->value) {
        prev = curr;
        curr = &((*curr)->next);
    }

    (*prev)->next = new;
    new->next = *curr;
}

// void in_order_insert(node **head, int val) {
//     node *new = malloc(sizeof(node));
//     node **prev = NULL;
//     node *curr = *head;

//     new->next = NULL;
//     new->value = val;

//     if (!*head) {
//         *head = new;
//         return;
//     }

//     // printf("looping");
//     while (curr && val > curr->value) {
//         *prev = curr;
//         curr = curr->next;
//     }

//     (*prev)->next = new;
//     new->next = curr;

//     // return head;

//     // printf("insert at:%d\n", curr->value);
// }

void append(node **head, int val) {
    node *new = malloc(sizeof(node)), **it;
    new->next = NULL;
    new->value = val;

    for (it = head; *it; it = &(*it)->next);
    *it = new;
}

void reverse(node **head) {
    node *prev = NULL;
    node *curr = *head;
    node *next;

    while (curr != NULL) {
        next = curr->next;
        curr->next = prev;
        prev = curr;
        curr = next;
    }

    *head = prev;
}

node *find(node *list, int key) {
    while (list && list->value != key)
        list = list->next;
    return list;
}

node *delete_list(node *list, node *target) {
    if (list == target) {
        return list->next;
    }

    node *prev = NULL;

    while (list != target) {
        prev = list;
        list = list->next;
    }

    prev->next = list->next;
    free(list);

    return list;
}

void free_list(node *list) {
    node *next;

    while (list != NULL) {
        printf("deleting: %d\n", list->value);
        next = list->next;
        free(list);
        list = next;
    }
}

int main() {
    node *list = NULL;

    append(&list, 99);
    list = insert_head(list, 10);
    list = insert_head(list, 20);
    print_list(list);

    reverse(&list);

    list = delete_list(list, find(list, 99));

    in_order_insert(&list, 15);

    print_list(list);

    free_list(list);

    return 0;
}

void insert_item_end ( node ** head , int val ) {
node * temp = malloc ( sizeof ( node ) ) ;
if (! temp ) return ;
temp -> value = val ;
temp -> next = NULL ;
if (* head ) {
node * ele = * head ;
for( ; ele -> next ; ele = ele -> next ) ;
ele -> next = temp ;
}
else
* head = temp ;
}

void append1(node *head, int val) {
    node *new = malloc(sizeof(node));
    new->next = NULL;
    new->value = val;

    while (head->next != NULL)
        head = head->next;

    head->next = new;
}

void append2(node **head, int val) {
    node *new = malloc(sizeof(node));
    new->next = NULL;
    new->value = val;

    if (!*head) {
        *head = new;
        return;
    }

    node *it = *head;

    while (it->next != NULL)
        it = it->next;

    it->next = new;
}

void append3(node **head, int val) {
    node *new = malloc(sizeof(node));
    new->next = NULL;
    new->value = val;

    node **it = head;
    while (*it != NULL)
        it = &((*it)->next); // it = &(**it).next;

    *it = new;
}