initial commit

c/armstrong-numbers/src/armstrong_numbers.c

@@ -0,0 +1,40 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "armstrong_numbers.h"
+
+static inline int power(int n, int p) {
+    int res=n;
+
+    /* useless here
+     * if (p==0)
+     *   return 1;
+     */
+    while (--p)
+        res*=n;
+    return res;
+}
+
+bool is_armstrong_number(int candidate)
+{
+    int p=1, r=0, tmp=candidate;
+
+    while (tmp/=10)
+        p++;
+
+    for (tmp=candidate; tmp; tmp /=10)
+        r+=power(tmp%10, p);
+    return r==candidate;
+}
+
+#ifdef UNIT_TEST
+int main(int ac, char **av)
+{
+    int arg=1, n;
+
+    for (; arg<ac; ++arg) {
+        n=atoi(av[arg]);
+        printf("armstrong(%d)=%d\n", n, is_armstrong_number(n));
+    }
+
+}
+#endif

c/armstrong-numbers/src/armstrong_numbers.h

@@ -0,0 +1,8 @@
+#ifndef ARMSTRONG_NUMBERS
+#define ARMSTRONG_NUMBERS
+
+#include <stdbool.h>
+
+bool is_armstrong_number(int candidate);
+
+#endif