Data commit

Task/Attractive-numbers/D/attractive-numbers.d

@@ -0,0 +1,51 @@
+import std.stdio;
+
+enum MAX = 120;
+
+bool isPrime(int n) {
+    if (n < 2) return false;
+    if (n % 2 == 0) return n == 2;
+    if (n % 3 == 0) return n == 3;
+    int d = 5;
+    while (d * d <= n) {
+        if (n % d == 0) return false;
+        d += 2;
+        if (n % d == 0) return false;
+        d += 4;
+    }
+    return true;
+}
+
+int primeFactorCount(int n) {
+    if (n == 1) return 0;
+    if (isPrime(n)) return 1;
+    int count;
+    int f = 2;
+    while (true) {
+        if (n % f == 0) {
+            count++;
+            n /= f;
+            if (n == 1) return count;
+            if (isPrime(n)) f = n;
+        } else if (f >= 3) {
+            f += 2;
+        } else {
+            f = 3;
+        }
+    }
+}
+
+void main() {
+    writeln("The attractive numbers up to and including ", MAX, " are:");
+    int i = 1;
+    int count;
+    while (i <= MAX) {
+        int n = primeFactorCount(i);
+        if (isPrime(n)) {
+            writef("%4d", i);
+            if (++count % 20 == 0) writeln;
+        }
+        ++i;
+    }
+    writeln;
+}