Data commit

Task/ISBN13-check-digit/Go/isbn13-check-digit.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+    "fmt"
+    "strings"
+    "unicode/utf8"
+)
+
+func checkIsbn13(isbn string) bool {
+    // remove any hyphens or spaces
+    isbn = strings.ReplaceAll(strings.ReplaceAll(isbn, "-", ""), " ", "")
+    // check length == 13
+    le := utf8.RuneCountInString(isbn)
+    if le != 13 {
+        return false
+    }
+    // check only contains digits and calculate weighted sum
+    sum := int32(0)
+    for i, c := range isbn {
+        if c < '0' || c > '9' {
+            return false
+        }
+        if i%2 == 0 {
+            sum += c - '0'
+        } else {
+            sum += 3 * (c - '0')
+        }
+    }
+    return sum%10 == 0
+}
+
+func main() {
+    isbns := []string{"978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"}
+    for _, isbn := range isbns {
+        res := "bad"
+        if checkIsbn13(isbn) {
+            res = "good"
+        }
+        fmt.Printf("%s: %s\n", isbn, res)
+    }
+}