CDE

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

@@ -0,0 +1,56 @@
+package main
+
+import (
+    "fmt"
+    "log"
+    "strconv"
+
+    "digit"
+)
+
+type testCase struct {
+    n           string
+    base        int
+    persistence int
+    root        int
+}
+
+var testCases = []testCase{
+    {"627615", 10, 2, 9},
+    {"39390", 10, 2, 6},
+    {"588225", 10, 2, 3},
+    {"393900588225", 10, 2, 9},
+}
+
+func root(n string, base int) (persistence, root int, err error) {
+    i, err := digit.Sum(n, base)
+    if err != nil {
+        return 0, 0, err
+    }
+    if len(n) == 1 {
+        return 0, int(i), nil
+    }
+    for {
+        persistence++
+        n := strconv.FormatInt(i, base)
+        if len(n) == 1 {
+            root = int(i)
+            break
+        }
+        i, _ = digit.Sum(n, base)
+    }
+    return
+}
+
+func main() {
+    for _, tc := range testCases {
+        p, r, err := root(tc.n, tc.base)
+        if err != nil {
+            log.Fatal(err)
+        }
+        if p != tc.persistence || r != tc.root {
+            log.Fatal("test case", tc)
+        }
+    }
+    fmt.Println("all tests passed")
+}