Added linked list implementation of queue.

CMakeLists.txt

@@ -4,3 +4,4 @@ add_subdirectory(arrays)
 add_subdirectory(linked_lists)
 add_subdirectory(linked_lists_redo)
 add_subdirectory(queue_array)
+add_subdirectory(queue_linked_list)

queue_linked_list/CMakeLists.txt

@@ -0,0 +1,7 @@
+cmake_minimum_required(VERSION 3.5)
+project(queue_linked_list_proj)
+
+set(SOURCE_FILES
+        main.c
+        )
+add_executable(queue_linked_list ${SOURCE_FILES})

queue_linked_list/main.c

@@ -0,0 +1,12 @@
+#include <stdlib.h>
+#include "queue.h"
+#include "queue.c"
+#include "tests_queue_linked_list.h"
+#include "tests_queue_linked_list.c"
+
+int main(int argc, char *argv[]) {
+
+  run_all_tests();
+
+  return EXIT_SUCCESS;
+}

queue_linked_list/queue.c

@@ -0,0 +1,85 @@
+queue * create_queue() {
+  queue *q = malloc(sizeof(node));
+  check_address(q);
+
+  q->head = 0;
+  q->tail = 0;
+
+  return q;
+}
+
+void enqueue(queue *q, int value) {
+  node *new_node = malloc(sizeof(node));
+  check_address(new_node);
+
+  new_node->value = value;
+  new_node->next = 0;
+
+  if (q->tail) {
+    q->tail->next = new_node;
+  }
+  q->tail = new_node;
+
+  if (q->head == 0) {
+    q->head = new_node;
+  }
+}
+
+const int dequeue(queue *q) {
+
+  if (empty(q)) {
+    printf("Unable to dequeue. Queue is empty.\n");
+    exit(EXIT_FAILURE);
+  }
+
+  int value = q->head->value;
+
+  node *temp = q->head;
+
+  if (q->tail == q->head) {
+    q->tail = 0;
+  }
+
+  q->head = q->head->next;
+  free(temp);
+
+  return value;
+}
+
+bool empty(queue *q) {
+  return q->head == 0;
+}
+
+void print_debug(queue *q) {
+  printf("Queue contents: ");
+
+  node *current = q->head;
+
+  while (current) {
+    printf("%d < ", current->value);
+    current = current->next;
+  }
+
+  printf("\n");
+}
+
+void check_address(void *addr) {
+  if (addr == 0) {
+    printf("Unable to allocate more memory.\n");
+    exit(EXIT_FAILURE);
+  }
+}
+
+void destroy_queue(queue *q) {
+
+  node *current = q->head;
+  node *temp = q->head;
+
+  while (current) {
+    temp = current;
+    current = current->next;
+    free(temp);
+  }
+
+  free(q);
+}

queue_linked_list/queue.h

@@ -0,0 +1,32 @@
+#include <stdbool.h>
+#include <stdio.h>
+
+#ifndef PROJECT_QUEUE_LINKED_LIST_H
+#define PROJECT_QUEUE_LINKED_LIST_H
+
+typedef struct Node {
+  int value;
+  struct Node *next;
+} node;
+
+typedef struct Queue {
+  node *head;
+  node *tail;
+} queue;
+
+// Creates new queue
+queue * create_queue();
+// Adds value at end of available storage
+void enqueue(queue *q, int value);
+// Returns value of least recently added element and removes it
+const int dequeue(queue *q);
+// Returns true if queue is empty
+bool empty(queue *q);
+// Prints contents of queue, starting with least recently added item first
+void print_debug(queue *q);
+// Checks address of allocated memory and exits if allocation failed
+void check_address(void *addr);
+// Free up memory used by queue
+void destroy_queue(queue *q);
+
+#endif //PROJECT_QUEUE_LINKED_LIST_H

queue_linked_list/tests_queue_linked_list.c

@@ -0,0 +1,30 @@
+void run_all_tests() {
+  test_empty();
+  test_all();
+}
+
+void test_empty() {
+  queue *q = create_queue();
+
+  assert(empty(q));
+
+  destroy_queue(q);
+}
+
+void test_all() {
+  queue *q = create_queue();
+
+  enqueue(q, 100);
+  assert(empty(q) == false);
+  assert(dequeue(q) == 100);
+  enqueue(q, 200);
+  enqueue(q, 300);
+  enqueue(q, 400);
+  assert(dequeue(q) == 200);
+  assert(dequeue(q) == 300);
+  assert(dequeue(q) == 400);
+
+  assert(empty(q));
+
+  destroy_queue(q);
+}

queue_linked_list/tests_queue_linked_list.h

@@ -0,0 +1,12 @@
+#include <stdio.h>
+#include <assert.h>
+
+#ifndef PROJECT_TESTS_QUEUE_LINKED_LIST_H
+#define PROJECT_TESTS_QUEUE_LINKED_LIST_H
+
+void run_all_tests();
+
+void test_empty();
+void test_all();
+
+#endif //PROJECT_TESTS_QUEUE_LINKED_LIST_H