update

easy/258.add-digits.go

@@ -0,0 +1,10 @@
+func addDigits(num int) int {
+	if num == 0 { // If sum of digits is divisable by 9, then num is divisable by 9.
+	// In fact, (num % 9) == [sum of digits] % 9
+		return 0
+	} else if n := nums % 9; n == 0 {
+		return 9
+	} else {
+		return n
+	}
+}

easy/263.ugly-number.go

@@ -0,0 +1,16 @@
+func isUgly(num int) bool {
+	if num <= 0 {
+		return false
+	}
+	for num & 1 == 0 {
+		num >>= 1
+	}
+	for num % 5 == 0 {
+		num /= 5
+	}
+	for num % 3 == 0 {
+		num /= 3
+	}
+	return num == 1
+}
+