Linked List

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

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

struct Node* push(struct Node *head, int x) {         // insert at beginning
    struct Node *n = malloc(sizeof(struct Node));
    n->data = x; n->next = head;
    return n;
}
struct Node* append(struct Node *head, int x) {       // insert at end
    struct Node *n = malloc(sizeof(struct Node));
    n->data = x; n->next = NULL;
    if (!head) return n;
    struct Node *t = head;
    while (t->next) t = t->next;
    t->next = n;
    return head;
}
struct Node* reverse(struct Node *head) {
    struct Node *prev = NULL, *cur = head, *nxt;
    while (cur) { nxt = cur->next; cur->next = prev; prev = cur; cur = nxt; }
    return prev;
}
void print(struct Node *h) {
    for (; h; h = h->next) printf("%d -> ", h->data);
    printf("NULL\n");
}

int main() {
    struct Node *head = NULL;
    head = append(head, 20);
    head = append(head, 30);
    head = push(head, 10);
    print(head);
    head = reverse(head);
    print(head);
    return 0;
}