Data commit

Task/Negative-base-numbers/D/negative-base-numbers.d

@@ -0,0 +1,62 @@
+import std.stdio;
+
+immutable DIGITS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+
+void main() {
+    driver(10, -2);
+    driver(146, -3);
+    driver(15, -10);
+    driver(13, -62);
+}
+
+void driver(long n, int b) {
+    string ns = encodeNegBase(n, b);
+    writefln("%12d encoded in base %3d = %12s", n, b, ns);
+
+    long p = decodeNegBase(ns, b);
+    writefln("%12s decoded in base %3d = %12d", ns, b, p);
+
+    writeln;
+}
+
+string encodeNegBase(long n, int b) in {
+    import std.exception : enforce;
+    enforce(b <= -1 && b >= -62);
+} body {
+    if (n==0) return "0";
+    char[] output;
+    long nn = n;
+    while (nn != 0) {
+        int rem = nn % b;
+        nn /= b;
+        if (rem < 0) {
+            nn++;
+            rem -= b;
+        }
+        output ~= DIGITS[rem];
+    }
+
+    import std.algorithm : reverse;
+
+    reverse(output);
+    return cast(string) output;
+}
+
+long decodeNegBase(string ns, int b) in {
+    import std.exception : enforce;
+    enforce(b <= -1 && b >= -62);
+} body {
+    if (ns == "0") return 0;
+    long total = 0;
+    long bb = 1;
+    foreach_reverse (c; ns) {
+        foreach(i,d; DIGITS) {
+            if (c==d) {
+                total += i * bb;
+                bb *= b;
+                break;
+            }
+        }
+    }
+    return total;
+}