C: pythagorean-triplet and saddle-point

c/pythagorean-triplet/src/pythagorean_triplet.c

@@ -0,0 +1,89 @@
+#include <malloc.h>
+
+#include "pythagorean_triplet.h"
+
+#define POOL_SIZE 10
+
+/* V1: initial version
+ * V2: cormetic changes
+ * V3: add pool for realloc instead of single realloc
+ */
+void free_triplets(triplets_t *t)
+{
+    free(t->triplets);
+    free(t);
+}
+
+static triplets_t *new_triplet()
+{
+    triplets_t *t=malloc(sizeof(triplets_t));
+    if (t) {
+        t->count = 0;
+        t->pool  = 0;
+        t->triplets = NULL;
+    }
+    return t;
+}
+
+static triplets_t *add_triplet(triplets_t *t, const uint16_t a, const uint16_t b,
+                               const uint16_t c)
+{
+    /* we may directly call add_triplet() without new_triplet. Not used here,
+     * but could be useful if triplets_with_sum() would return NULL when no
+     * solution found.
+     */
+    if (! (t || (t = new_triplet())))
+        return NULL;
+
+    if (t->count == t->pool) {
+        t->pool += POOL_SIZE;
+        if (!(t->triplets = realloc(t->triplets, sizeof(triplets_t) +
+                                    t->pool * sizeof(triplet_t)))) {
+            free(t);
+            return NULL;
+        }
+    }
+    t->triplets[t->count] = (triplet_t) {a, b, c};
+    t->count++;
+    return t;
+}
+
+/* algorithm from : https://stackoverflow.com/a/2818750/3079831
+ */
+triplets_t *triplets_with_sum(uint16_t sum)
+{
+    int a, b, c;
+    triplets_t *t;
+
+    if (!(t = new_triplet()))
+        return NULL;
+    if (sum%2)
+        return t;
+
+    for (a = 1; a <= sum/3; a++) {
+        for (b = a + 1; b <= sum/2; b++) {
+            c = sum - a - b;
+            if (a*a + b*b == c*c)
+                if (!(t = add_triplet(t, a, b, c)))
+                    return NULL;
+        }
+    }
+    return t;
+}
+
+/* See GNUmakefile below for explanation
+ * https://github.com/braoult/exercism/blob/master/c/templates/GNUmakefile
+ */
+#ifdef UNIT_TEST
+int main(int ac, char **av)
+{
+    int arg=1;
+    resistor_band_t i[2];
+
+    for (; arg<ac-1; ++arg, ++arg) {
+        *i=atoi(av[arg]);
+        *(i+1)=atoi(av[arg+1]);
+        printf("color(%d, %d)=%d\n", i[0], i[1], color_code(i));
+    }
+}
+#endif

c/pythagorean-triplet/src/pythagorean_triplet.h

@@ -0,0 +1,34 @@
+#ifndef PYTHAGOREAN_TRIPLET
+#define PYTHAGOREAN_TRIPLET
+#include <stdlib.h>
+#include <stdint.h>
+
+typedef struct triplet {
+    uint16_t a;
+    uint16_t b;
+    uint16_t c;
+} triplet_t;
+
+typedef struct triplets {
+    size_t count;
+    size_t pool;
+    triplet_t *triplets;
+} triplets_t;
+
+triplets_t *triplets_with_sum(uint16_t sum);
+void free_triplets(triplets_t *triplet);
+
+/* See GNUmakefile below for explanation
+ * https://github.com/braoult/exercism/blob/master/c/templates/GNUmakefile
+ */
+#if defined UNIT_TEST || defined DEBUG
+#include <stdio.h>
+#include <stdlib.h>
+#endif
+
+#ifdef  TESTALL
+#undef  TEST_IGNORE
+#define TEST_IGNORE() {}
+#endif
+
+#endif