tasks a-s

Task/Remove-duplicate-elements/C/remove-duplicate-elements-1.c

@@ -0,0 +1,33 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct list_node {int x; struct list_node *next;};
+typedef struct list_node node;
+
+node * uniq(int *a, unsigned alen)
+ {if (alen == 0) return NULL;
+  node *start = malloc(sizeof(node));
+  if (start == NULL) exit(EXIT_FAILURE);
+  start->x = a[0];
+  start->next = NULL;
+
+  for (int i = 1 ; i < alen ; ++i)
+     {node *n = start;
+      for (;; n = n->next)
+         {if (a[i] == n->x) break;
+          if (n->next == NULL)
+             {n->next = malloc(sizeof(node));
+              n = n->next;
+              if (n == NULL) exit(EXIT_FAILURE);
+              n->x = a[i];
+              n->next = NULL;
+              break;}}}
+
+  return start;}
+
+int main(void)
+   {int a[] = {1, 2, 1, 4, 5, 2, 15, 1, 3, 4};
+    for (node *n = uniq(a, 10) ; n != NULL ; n = n->next)
+        printf("%d ", n->x);
+    puts("");
+    return 0;}

Task/Remove-duplicate-elements/C/remove-duplicate-elements-2.c

@@ -0,0 +1,59 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+
+/* Returns `true' if element `e' is in array `a'. Otherwise, returns `false'.
+ * Checks only the first `n' elements. Pure, O(n).
+ */
+bool elem(int *a, size_t n, int e)
+{
+    for (size_t i = 0; i < n; ++i)
+        if (a[i] == e)
+            return true;
+
+    return false;
+}
+
+/* Removes the duplicates in array `a' of given length `n'. Returns the number
+ * of unique elements. In-place, order preserving, O(n ^ 2).
+ */
+size_t nub(int *a, size_t n)
+{
+    size_t m = 0;
+
+    for (size_t i = 0; i < n; ++i)
+        if (!elem(a, m, a[i]))
+            a[m++] = a[i];
+
+    return m;
+}
+
+/* Out-place version of `nub'. Pure, order preserving, alloc < n * sizeof(int)
+ * bytes, O(n ^ 2).
+ */
+size_t nub_new(int **b, int *a, size_t n)
+{
+    int *c = malloc(n * sizeof(int));
+    memcpy(c, a, n * sizeof(int));
+    int m = nub(c, n);
+    *b = malloc(m * sizeof(int));
+    memcpy(*b, c, m * sizeof(int));
+    free(c);
+    return m;
+}
+
+int main(void)
+{
+    int a[] = {1, 2, 1, 4, 5, 2, 15, 1, 3, 4};
+    int *b;
+
+    size_t n = nub_new(&b, a, sizeof(a) / sizeof(a[0]));
+
+    for (size_t i = 0; i < n; ++i)
+        printf("%d ", b[i]);
+    puts("");
+
+    free(b);
+    return 0;
+}

Task/Remove-duplicate-elements/C/remove-duplicate-elements-3.c

@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int icmp(const void *a, const void *b)
+{
+#define _I(x) *(int*)x
+	return _I(a) < _I(b) ? -1 : _I(a) > _I(b);
+#undef _I
+}
+
+/* filter items in place and return number of uniques.  if a separate
+   list is desired, duplicate it before calling this function */
+int uniq(int *a, int len)
+{
+	int i, j;
+	qsort(a, len, sizeof(int), icmp);
+	for (i = j = 0; i < len; i++)
+		if (a[i] != a[j]) a[++j] = a[i];
+	return j + 1;
+}
+
+int main()
+{
+	int x[] = {1, 2, 1, 4, 5, 2, 15, 1, 3, 4};
+	int i, len = uniq(x, sizeof(x) / sizeof(x[0]));
+	for (i = 0; i < len; i++) printf("%d\n", x[i]);
+
+	return 0;
+}