Fix 56 - Add algorithm for doubly linked list in C

C/Doubly Linked List/doublyLinkedList.c

@@ -0,0 +1,178 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+typedef struct node{
+	int num;
+	struct node *previous_node;
+	struct node *next_node;
+} node;
+
+node* reverse_list(node *dll)
+{
+	node *current_node = dll;
+	node *aux_node = NULL;
+    node *start = NULL;
+
+	while(current_node->next_node != NULL)
+	{
+		current_node = current_node->next_node;
+	}
+
+	start = current_node;
+
+	do
+	{
+		aux_node = current_node->next_node;
+		current_node->next_node = current_node->previous_node;
+		current_node->previous_node = aux_node;
+		current_node = current_node->next_node;
+	}
+	while(current_node != NULL);
+
+	return start;
+}
+
+node* get_node_by_index(node *dll, int index)
+{
+    if(index < 0)
+    {
+        return NULL;
+    }
+
+    for(int i = 0; i != index; i++)
+    {
+        if(dll->next_node != NULL)
+        {
+            dll = dll->next_node;
+        }
+        else
+        {
+            return NULL;
+        }
+    }
+
+    return dll;
+}
+
+node* swap_nodes(node *dll, int first_element, int second_element)
+{
+    node *first_node = NULL;
+    node *second_node = NULL;
+
+	if(first_element < 0 || second_element < 0)
+	{
+		return NULL;
+	}
+
+	first_node = get_node_by_index(dll, first_element);
+    second_node = get_node_by_index(dll, second_element);
+
+    first_node->previous_node->num = first_node->previous_node->num + second_node->previous_node->num;
+    second_node->previous_node->num = first_node->previous_node->num - second_node->previous_node->num;
+    first_node->previous_node->num = first_node->previous_node->num - second_node->previous_node->num;
+
+    return dll;
+}
+
+node* sort_list(node *dll)
+{
+    bool swapped;
+
+    while(dll->previous_node != NULL)
+    {
+        dll = dll->previous_node;
+    }
+
+    do
+    {
+        swapped = false;
+        for(int i = 1; dll->next_node != NULL; i++)
+        {
+            if(dll->num > dll->next_node->num)
+            {
+                dll->num = dll->num + dll->next_node->num;
+                dll->next_node->num = dll->num - dll->next_node->num;
+                dll->num = dll->num - dll->next_node->num;
+                swapped = true;
+            }
+            dll = dll->next_node;
+        }
+
+        while(dll->previous_node != NULL)
+        {
+            dll = dll->previous_node;
+        }
+    }
+    while(swapped == true);
+
+    return dll;
+}
+
+node* add_node(node *dll, int num)
+{
+    node* start = NULL;
+
+    if(dll == NULL)
+    {
+        start = malloc(sizeof(node));
+    }
+    else
+    {
+        while(dll->next_node != NULL)
+        {
+            dll = dll->next_node;
+        }
+        dll->next_node = malloc(sizeof(node));
+        start = dll->next_node;
+    }
+
+    start->previous_node = dll;
+    start->num = num;
+
+    return start;
+}
+
+node* slice_list(node *dll, int first_element, int last_element)
+{
+    node *slice = NULL;
+    node *start = NULL;
+
+    while(dll->previous_node != NULL)
+    {
+        dll = dll->previous_node;
+    }
+
+    if(first_element < 0 || last_element < 0)
+    {
+        return NULL;
+    }
+
+    for(int i = 0; i <= last_element; i++)
+    {
+        if(i >= first_element)
+        {
+            slice = add_node(slice, dll->num);
+        }
+        dll = dll->next_node;
+    }
+
+    start = slice;
+    while(start->previous_node != NULL)
+    {
+        start = start->previous_node;
+    }
+
+    return start;
+}
+
+void print_list(node *dll)
+{
+    for(int i = 0; dll != NULL; i++)
+    {
+        printf("Node: %d Num: %d\n", i, dll->num);
+        dll = dll->next_node;
+    }
+
+    return;
+}