From aa9377d5fc63677aa5977e665ece8e596caf2dfc Mon Sep 17 00:00:00 2001
From: Valentin Gehrke <madmaurice@zom.bi>
Date: Thu, 11 Feb 2016 18:20:26 +0100
Subject: [PATCH] EPA: double linked list.

---
 doublelinkedlist.c | 144 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 144 insertions(+)
 create mode 100644 doublelinkedlist.c

diff --git a/doublelinkedlist.c b/doublelinkedlist.c
new file mode 100644
index 0000000..0c44f6a
--- /dev/null
+++ b/doublelinkedlist.c
@@ -0,0 +1,144 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+
+typedef struct node {
+    int element;
+    struct node* prev;
+    struct node* next;
+} *Nodeptr, Node;
+
+typedef struct list {
+    Nodeptr head, tail, current_node;
+} *List;
+
+List dll_create();
+void dll_insertafter(List l, int element);
+int dll_find_next(List l);
+int dll_find_prev(List l);
+void dll_insertbefore(List l, int element);
+int dll_find(List l, int element);
+void dll_find_first(List l);
+void dll_find_last(List l);
+int dll_retrieve(List l);
+void dll_update(List l, int element);
+void dll_clear(List l);
+
+List dll_create() {
+    List l = malloc(sizeof(struct list));
+    l->head = NULL;
+    l->tail = NULL;
+    l->current_node = NULL;
+    return l;
+}
+
+void dll_insertafter(List l, int element) {
+    Nodeptr n = malloc(sizeof(Node));
+    n->element = element;
+    n->next = NULL;
+    n->prev = NULL;
+    if(l->head == NULL) {
+        l->head = l->tail = n;
+    } else {
+        n->next = l->current_node->next;
+        if(l->current_node == l->tail) {
+            l->tail = n;
+        } else {
+            l->current_node->next->prev = n;
+        }
+        l->current_node->next = n;
+        n->prev = l->current_node;
+    }
+    l->current_node = n;
+}
+
+int dll_find_next(List l) {
+    if(l->current_node == l->tail) return 0;
+    l->current_node = l->current_node->next;
+    return 1;
+}
+
+int dll_find_prev(List l) {
+    if(l->current_node == l->head) return 0;
+    l->current_node = l->current_node->prev;
+    return 1;
+}
+
+void dll_insertbefore(List l, int element) {
+    if(l->head == NULL) {
+        dll_insertafter(l,element);
+    } else if(!dll_find_prev(l)) {
+        Nodeptr n = malloc(sizeof(Node));
+        n->element = element;
+        n->next = l->head;
+        n->prev = NULL;
+        l->head->prev = n;
+        l->head = n;
+        l->current_node = n;
+    } else {
+        dll_insertafter(l,element);
+    }
+}
+
+int dll_find(List l, int element) {
+    dll_find_first(l);
+    do {
+        if(dll_retrieve(l) == element) return 1;
+    } while(dll_find_next(l));
+    return 0;
+}
+
+void dll_find_first(List l) {
+    assert(l->head != NULL);
+    l->current_node = l->head;
+}
+
+void dll_find_last(List l) {
+    assert(l->tail != NULL);
+    l->current_node = l->tail;
+}
+
+int dll_retrieve(List l) {
+    assert(l->current_node != NULL);
+    return l->current_node->element;
+}
+
+void dll_update(List l, int element) {
+    assert(l->current_node != NULL);
+    l->current_node->element = element;
+}
+
+void dll_clear(List l) {
+    Nodeptr tmp, iter;
+    iter = l->head;
+    while(iter != NULL) {
+        tmp = iter;
+        iter = iter->next;
+        free(tmp);
+    }
+
+    l->head = NULL;
+    l->tail = NULL;
+    l->current_node = NULL;
+}
+
+int main( int argc, char *argv[] ) {
+	List l = dll_create();
+    for(int i = 0; i < 10; i++) {
+        dll_insertafter(l,i);
+    }
+
+    dll_find(l,5);
+
+    do {
+        printf("%d\n", dll_retrieve(l));
+    } while(dll_find_next(l));
+
+    dll_find_first(l);
+    do {
+        printf("%d\n", dll_retrieve(l));
+    } while(dll_find_next(l));
+
+    dll_clear(l);
+	return 0;
+}