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

typedef struct _Node
{
  int value;
  struct _Node *next;
} Node;

Node *createNode(int value)
{
  Node *newNode = (Node *)malloc(sizeof(Node));
  newNode->value = value;
  newNode->next = NULL;
  return newNode;
}

void pushFront(Node **list, int value)
{
  Node *nextElem = createNode(value);
  nextElem->next = (*list);
  (*list) = nextElem;
}

Node *getTail(Node *list)
{
  if (list == NULL)
    return NULL;
  while (list->next)
    list = list->next;
  return list;
}

Node* getPenultimate(Node* list)
{
    while(list->next->next)
        list=list->next;
    return list;
}

void pushBack(Node **list, int value)
{
  Node *tail = getTail((*list));
  Node *elem = createNode(value);
  elem->next = NULL;
  tail->next = elem;
}

void popFront(Node **list)
{
  if ((*list) == NULL)
    return;
  Node *next = (*list)->next;
  free((*list));
  (*list) = next;
}

void popBack(Node **list)
{
  if ((*list) == NULL)
    return;
  Node* tail = getPenultimate((*list));
  free(tail->next);
  tail->next = NULL;
}

int main()
{
  Node *n = createNode(12);
  printf("front value after createNode(12): %d \n", n->value);
  pushFront(&n, 32);
  printf("tail value after  pushFront(&n, 32): %d \n", getTail(n)->value);
  pushBack(&n, 64);
  printf("tail value after pushBack(&n, 64): %d \n", getTail(n)->value);
  printf("front value after pushBack(&n, 64): %d \n", n->value);
  popBack(&n);
  printf("tail value after popBack(&n): %d \n", getTail(n)->value);
  popFront(&n);
  printf("front value after popFront(&n): %d \n", n->value);
  return 0;
}