Data commit

Task/Digital-root/Go/digital-root.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"strconv"
+)
+
+func Sum(i uint64, base int) (sum int) {
+	b64 := uint64(base)
+	for ; i > 0; i /= b64 {
+		sum += int(i % b64)
+	}
+	return
+}
+
+func DigitalRoot(n uint64, base int) (persistence, root int) {
+	root = int(n)
+	for x := n; x >= uint64(base); x = uint64(root) {
+		root = Sum(x, base)
+		persistence++
+	}
+	return
+}
+
+// Normally the below would be moved to a *_test.go file and
+// use the testing package to be runnable as a regular test.
+
+var testCases = []struct {
+	n           string
+	base        int
+	persistence int
+	root        int
+}{
+	{"627615", 10, 2, 9},
+	{"39390", 10, 2, 6},
+	{"588225", 10, 2, 3},
+	{"393900588225", 10, 2, 9},
+	{"1", 10, 0, 1},
+	{"11", 10, 1, 2},
+	{"e", 16, 0, 0xe},
+	{"87", 16, 1, 0xf},
+	// From Applesoft BASIC example:
+	{"DigitalRoot", 30, 2, 26}, // 26 is Q base 30
+	// From C++ example:
+	{"448944221089", 10, 3, 1},
+	{"7e0", 16, 2, 0x6},
+	{"14e344", 16, 2, 0xf},
+	{"d60141", 16, 2, 0xa},
+	{"12343210", 16, 2, 0x1},
+	// From the D example:
+	{"1101122201121110011000000", 3, 3, 1},
+}
+
+func main() {
+	for _, tc := range testCases {
+		n, err := strconv.ParseUint(tc.n, tc.base, 64)
+		if err != nil {
+			log.Fatal(err)
+		}
+		p, r := DigitalRoot(n, tc.base)
+		fmt.Printf("%12v (base %2d) has additive persistence %d and digital root %s\n",
+			tc.n, tc.base, p, strconv.FormatInt(int64(r), tc.base))
+		if p != tc.persistence || r != tc.root {
+			log.Fatalln("bad result:", tc, p, r)
+		}
+	}
+}