title: Swift String init ambiguous(which String.init method does this code call?)
body: <p>It's a leetcode problem: 168. Excel Sheet Column Title @
  <a href="https://leetcode.com/problems/excel-sheet-column-title/" rel="nofollow">https://leetcode.com/problems/excel-sheet-column-title/</a></p>
  
  <hr>
  
  <p>The code works fine at my mac, 
  but got compile error at leetcode:<br/>
  <b>Line 5: ambiguous use of 'init'</b><br/>
  So, please tell me which String.init method does this code call?<br/></p>
  
  <pre><code>String(UnicodeScalar(val))
  </code></pre>
  
  And how I can solve this issue? 
  
  <p><br/></p>
  
  <pre><code>class Solution {
      func convertToTitle(n: Int) -&gt; String {
          var alphabet = [String]()
          var result = ""
          alphabet = (UnicodeScalar("A").value...UnicodeScalar("Z").value).map({(val: UInt32) -&gt; String in return String(UnicodeScalar(val)); })
          var num = n
          while num != 0 {
              num -= 1
              result = alphabet[num % 26] + result
              num /= 26
          }
          return result
      }}
  </code></pre>