Initial data commit

Task/Queue-Definition/C/queue-definition-2.c

@@ -0,0 +1,43 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct node_t node_t, *node, *queue;
+struct node_t { int val; node prev, next; };
+
+#define HEAD(q) q->prev
+#define TAIL(q) q->next
+queue q_new()
+{
+    node q = malloc(sizeof(node_t));
+    q->next = q->prev = 0;
+    return q;
+}
+
+int empty(queue q)
+{
+    return !HEAD(q);
+}
+
+void enqueue(queue q, int n)
+{
+    node nd = malloc(sizeof(node_t));
+    nd->val = n;
+    if (!HEAD(q)) HEAD(q) = nd;
+    nd->prev = TAIL(q);
+    if (nd->prev) nd->prev->next = nd;
+    TAIL(q) = nd;
+    nd->next = 0;
+}
+
+int dequeue(queue q, int *val)
+{
+    node tmp = HEAD(q);
+    if (!tmp) return 0;
+    *val = tmp->val;
+
+    HEAD(q) = tmp->next;
+    if (TAIL(q) == tmp) TAIL(q) = 0;
+    free(tmp);
+
+    return 1;
+}