tasks a-s

Task/Prime-decomposition/D/prime-decomposition.d

@@ -0,0 +1,37 @@
+import std.traits: Unqual;
+
+Unqual!T[] decompose(T)(T number) /*pure nothrow*/
+in {
+    assert(number > 1);
+} body {
+    alias UT = Unqual!T;
+    typeof(return) result;
+    UT n = number;
+
+    for (UT i = 2; n % i == 0;) {
+        result ~= i;
+        n /= i;
+    }
+    for (UT i = 3; n >= i * i; i += 2) {
+        while (n % i == 0) {
+            result ~= i;
+            n /= i;
+        }
+    }
+
+    if (n != 1)
+        result ~= n;
+    return result;
+}
+
+void main() {
+    import std.stdio, std.bigint, std.algorithm;
+
+    foreach (immutable n; 2 .. 10)
+        writeln(decompose(n));
+
+    writeln(decompose(1023 * 1024));
+    writeln(decompose(BigInt(2 * 3 * 5 * 7 * 11 * 11 * 13 * 17)));
+    writeln(decompose(BigInt(16860167264933UL) * 179951));
+    writeln(group(decompose(BigInt(2) ^^ 100_000)));
+}