title: repeat string n times in Kotlin
body: <p>I want to create a <code>string</code> which would contain a <code>*</code> symbol <code>n</code> times.
  I only see this way:</p>
  
  <pre><code>val s = ""
  val n = 100
  for (j in 0 until n) {
      s += "*"
  }
  </code></pre>
  
  <p>But it looks ugly and it has a O(n^2) time complexity. Is there a way in Kotlin to do that without a loop with better time complexity?</p>