From a8c603e8e58109869cdbc2cb1c344183c7cdff3b Mon Sep 17 00:00:00 2001
From: Dan Buch <daniel.buch@gmail.com>
Date: Wed, 13 Apr 2016 12:07:56 -0400
Subject: [PATCH] ex18

---
 lcthw-remnants-2/.gitignore |  23 +-------
 lcthw-remnants-2/ex18.c     | 111 ++++++++++++++++++++++++++++++++++++
 lcthw-remnants-2/runtests   |   8 +++
 3 files changed, 122 insertions(+), 20 deletions(-)
 create mode 100644 lcthw-remnants-2/ex18.c

diff --git a/lcthw-remnants-2/.gitignore b/lcthw-remnants-2/.gitignore
index 976020d..6f17809 100644
--- a/lcthw-remnants-2/.gitignore
+++ b/lcthw-remnants-2/.gitignore
@@ -1,20 +1,3 @@
-ex1
-ex3
-ex4
-ex5
-ex6
-ex7
-ex8
-ex9
-ex9-ec
-ex10
-ex11
-ex12
-ex13
-ex14
-ex15
-ex16
-ex17
-db.dat
-ex17-ec
-ex17-ec2
+*.dat
+ex*
+!ex*.c
diff --git a/lcthw-remnants-2/ex18.c b/lcthw-remnants-2/ex18.c
new file mode 100644
index 0000000..4de105a
--- /dev/null
+++ b/lcthw-remnants-2/ex18.c
@@ -0,0 +1,111 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+
+/** Our old friend die from ex17. */
+void die(const char *message)
+{
+  if(errno) {
+    perror(message);
+  } else {
+    printf("ERROR: %s\n", message);
+  }
+
+  exit(1);
+}
+
+// a typedef creates a fake type, in this
+// case for a function pointer
+typedef int (*compare_cb)(int a, int b);
+
+/**
+ * A classic bubble sort function that uses the
+ * compare_cb to do the sorting.
+ */
+int *bubble_sort(int *numbers, int count, compare_cb cmp)
+{
+  int temp = 0;
+  int i = 0;
+  int j = 0;
+  int *target = malloc(count * sizeof(int));
+
+  if(!target) die("Memory error.");
+
+  memcpy(target, numbers, count * sizeof(int));
+
+  for(i = 0; i < count; i++) {
+    for(j = 0; j < count - 1; j++) {
+      if(cmp(target[j], target[j+1]) > 0) {
+        temp = target[j+1];
+        target[j+1] = target[j];
+        target[j] = temp;
+      }
+    }
+  }
+
+  return target;
+}
+
+int sorted_order(int a, int b)
+{
+  return a - b;
+}
+
+int reverse_order(int a, int b)
+{
+  return b - a;
+}
+
+int strange_order(int a, int b)
+{
+  if(a == 0 || b == 0) {
+    return 0;
+  } else {
+    return a % b;
+  }
+}
+
+/**
+ * Used to test that we are sorting things correctly
+ * by doing the sort and printing it out.
+ */
+void test_sorting(int *numbers, int count, compare_cb cmp)
+{
+  int i = 0;
+  int *sorted = bubble_sort(numbers, count, cmp);
+
+  if(!sorted) die("Failed to sort as requested.");
+
+  for(i = 0; i < count; i++) {
+    printf("%d ", sorted[i]);
+  }
+  printf("\n");
+
+  free(sorted);
+}
+
+int main(int argc, char *argv[])
+{
+  if(argc < 2) die("USAGE: ex18 4 3 1 5 6");
+
+  int count = argc - 1;
+  int i = 0;
+  char **inputs = argv + 1;
+
+  int *numbers = malloc(count * sizeof(int));
+  if(!numbers) die("Memory error.");
+
+  for(i = 0; i < count; i++) {
+    numbers[i] = atoi(inputs[i]);
+  }
+
+  test_sorting(numbers, count, sorted_order);
+  test_sorting(numbers, count, reverse_order);
+  test_sorting(numbers, count, strange_order);
+
+  free(numbers);
+
+  return 0;
+}
+
diff --git a/lcthw-remnants-2/runtests b/lcthw-remnants-2/runtests
index c8f6e28..0640266 100755
--- a/lcthw-remnants-2/runtests
+++ b/lcthw-remnants-2/runtests
@@ -18,6 +18,14 @@ test_ex17-ec() {
   echo "OK"
 }
 
+test_ex18() {
+  local output=$(./ex18 4 1 7 3 2 0 8)
+  [[ "${output}" =~ '0 1 2 3 4 7 8' ]]
+  [[ "${output}" =~ '8 7 4 3 2 1 0' ]]
+  [[ "${output}" =~ '3 4 2 7 1 0 8' ]]
+  echo "OK"
+}
+
 main() {
   for ex in $(./list-exercises) ; do
     func_name="test_${ex}"