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

typedef struct LL_NODE {
  struct LL_NODE *next, *prev;
  int data;
} ll_node;


//inserts node containig data before/after node *where. if where is NULL then creates a
//standalone node, returns address of new node
ll_node *ll_insert(int data, ll_node *where, int after)
{
  ll_node *temp = NULL;

  if((temp = (ll_node *)malloc(sizeof(ll_node))) == NULL) {
    fprintf(stderr, "malloc failed!!\n");
    return NULL;
  }
  temp->data = data;

  if(where == NULL) {
    temp->prev = NULL;
    temp->next = NULL;
    return temp;
  }

  if(after) {
    temp->next = where->next;
    temp->prev = where;
    where->next = temp;
    if(temp->next != NULL) {
      temp->next->prev = temp;
    }
  } else {
    temp->next = where;
    temp->prev = where->prev;
    where->prev = temp;
    if(temp->prev != NULL) {
      temp->prev->next = temp;
    }
  }

  return temp;
}

//pretty obvious
void ll_remove(ll_node *node)
{
  if(node != NULL) {
    if(node->prev != NULL) node->prev->next = node->next;
    if(node->next != NULL) node->next->prev = node->prev;
    free(node);
  }
}

//starting at *start goes in dir and looks for data, returns node containg data
ll_node *ll_find(int data, ll_node *start, int dir)
{
  ll_node *curNode = start;

  while(curNode != NULL) {
    if(curNode->data == data) break;

    if(dir)
      curNode = curNode->next;
    else
      curNode = curNode->prev;
  }

  return curNode;
}

void print(ll_node *start)
{
  ll_node *curNode = start;

  while(curNode != NULL) {
    printf("[%d]", curNode->data);
    curNode = curNode->next;
  }
  printf("\n");
}

int main()
{
  int i;
  ll_node *top = NULL, *cur = NULL;
  
  //put '1' through '10' in list
  top = ll_insert(1, NULL, 0);
  cur = top;
  for(i=2;i<11;i++) 
    cur = ll_insert(i, cur, 1);
  print(top);

  //remove 5
  ll_remove(ll_find(5, top, 1));
  print(top);

  //add it
  ll_insert(5, ll_find(6, top, 1), 0);
  print(top);

  //really should clear up but this is data structure test
  //not a good program, let windows clear up for me.
  return 0;
}