1 files changed, 112 insertions, 0 deletions
diff --git a/src/01/02b/doubly_linked_list.c b/src/01/02b/doubly_linked_list.c
new file mode 100644
index 0000000..88e49ee
--- /dev/null
+++ b/src/01/02b/doubly_linked_list.c
@@ -0,0 +1,112 @@
+#include "doubly_linked_list.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+Node *initialize(int data) {
+  Node *node = malloc(sizeof(Node));
+  node->data = data;
+  node->next = NULL;
+  node->prev = NULL;
+  return node;
+}
+
+Node *add(Node *head, int data) {
+  Node *tail;
+  Node *tmp = head;
+
+  while(tmp) {
+    if (!tmp->next)
+      break;
+    tmp = tmp->next;
+  }
+  tail = tmp;
+  tail->next = initialize(data);
+  tail->next->prev = tail;
+  return tail->next;
+}
+
+Node *get(Node *from, int index) {
+  if (!from || index < 0) return NULL;
+
+  while(index > 0 && from){
+    from = from->next;
+    index--;
+  }
+  return from;
+}
+
+static int size(Node *head) {
+  int i = 0;
+  for (Node *tmp = head; tmp && tmp != NULL; tmp = tmp->next) i++;
+  return i;
+}
+
+static void assign_next(Node *self, Node *other) {
+  if (self)
+    self->next = other;
+
+  if (other)
+    other->prev = self;
+}
+
+static void assign_prev(Node *self, Node *other) {
+  if (self)
+    self->prev = other;
+
+  if (other)
+    other->next = self;
+}
+
+void swap(Node *x, Node *y) {
+  if (x == y) return;
+  if (!x || !y) return;
+  if (x->prev == y && y->next == x) return swap(y, x);
+
+  Node *xp = x->prev, *xn = x->next, *yp = y->prev, *yn = y->next;
+
+  // if adjacent
+  if (x->next == y && y->prev == x) {
+    assign_next(x, yn);
+    assign_prev(x, y);
+    assign_prev(y, xp);
+  } else {
+    assign_prev(x, yp);
+    assign_next(x, yn);
+    assign_prev(y, xp);
+    assign_next(y, xn);
+  }
+}
+
+Node *reverse(Node *head) {
+  Node *tmp = NULL;
+  Node *current = head;
+
+  while (current != NULL) {
+    tmp = current->prev;
+    current->prev = current->next;
+    current->next = tmp;
+    current = current->prev;
+  }
+  return tmp ? tmp->prev : head;
+}
+
+static void print(Node *node) {
+  if (node->prev && node->next)
+    printf("%d <- %d -> %d\n", node->prev->data, node->data, node->next->data);
+  else if (node->next)
+    printf("nil <- %d -> %d\n", node->data, node->next->data);
+  else
+    printf("%d <- %d -> nil\n", node->prev->data, node->data);
+}
+
+static void inspect(Node *node) {
+  if (!node) return;
+
+  printf("*******\n");
+  while (node) {
+    print(node);
+    node = node->next;
+  }
+  printf("*******\n");
+}
+