Added a text file for the editor race for UNIX 102.

unix102/Makefile

@@ -1,3 +1,3 @@
-FILES = index.html cheatsheet.pdf unix101.pdf vim_exercise.tar appender.sh tickets_email.sh
+FILES = index.html cheatsheet.pdf unix101.pdf vim_exercise.tar appender.sh tickets_email.sh queue.txt
 RELDIR = unix102/
 include ../common.mk

unix102/index.xml

@@ -12,6 +12,9 @@
       as well as some extracurricular content for you to review in your free
       time.  
     </p>
+    <p>
+      The text file for the great editor race is available <a href="queue">here</a>.
+    </p>
     <p>
       To begin with the first exercise, you will need the following file.
       To download it, execute the following command:

unix102/queue.txt

@@ -0,0 +1,100 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct list {
+   int head;
+   struct list *tail;
+};
+
+typedef struct list list;
+
+typedef struct {
+   list *front;
+   list *back;
+} queue;
+
+void list_free(list *lst) {
+   list *p;
+
+   while (lst != NULL) {
+      p = lst;
+      lst = lst->tail;
+      free(p);
+   }
+}
+
+list * cons(int val, list *lst) {
+   list *new = malloc(sizeof(list));
+   if (new == NULL) abort();
+
+   new->head = val;
+   new->tail = lst;
+
+   return new;
+}
+
+void list_print(list *lst) {
+   list *p = lst;
+
+   while (p != NULL) {
+      printf("%d ", p->head);
+      p = p->tail;
+   }
+}
+
+queue * make_queue() {
+   queue *new = malloc(sizeof(queue));
+   if (new == NULL) abort();
+
+   new->front = NULL;
+   new->back = NULL;
+
+   return new;
+}
+
+void push(int val, queue *q) {
+   if (q->front == NULL) { // empty queue
+      q->front = cons(val, NULL);
+      q->back = q->front;
+   }
+
+   else {
+      list *new = cons(val, NULL);
+      (q->back)->tail = new;
+      q->back = new;
+   }
+}
+
+int pop(queue *q) {
+   int val = (q->front)->head;
+   list *newhead = (q->front)->tail;
+   (q->front)->tail = NULL;
+   list_free(q->front);
+   q->front = newhead;
+
+   return val;
+}
+
+void queue_print(queue *q) {
+   printf("back ");
+   list_print(q->front);
+   printf("front\n");
+}
+
+void queue_free(queue *q) {
+   list_free(q->front);
+   free(q);
+}
+
+int main() {
+   queue *q = make_queue();
+   push(5, q);
+   push(3, q);
+   push(1, q);
+   queue_print(q);
+   printf("popped %d!\n", pop(q));
+   queue_print(q);
+   queue_free(q);
+
+   return 0;
+}