Merge pull request soapyigu#278 from iHackSubhodip/master

[String] Solution for License Key Formatting.

Author: soapyigu

String/LicenseKeyFormatting.swift

@@ -0,0 +1,35 @@
+/**
+ * Question Link: https://leetcode.com/problems/license-key-formatting/
+ * Primary idea: traverse the array formatted string from end. Insert the dash into the String as per given K, else insert the elements at index 0.
+ *
+ * Time Complexity: O(n), Space Complexity: O(1)
+ *
+ */
+
+class LicenseKeyFormatting {
+    func licenseKeyFormatting(_ S: String, _ K: Int) -> String {
+        guard S.count > 0 && K > 0 else{
+            return ""
+        }
+        
+        let upperCaseString = Array(S.uppercased())
+        var result = [Character](), n = K
+        
+        for i in stride(from: S.count - 1, through: 0, by: -1){
+            let aCharacter = upperCaseString[i]
+            guard aCharacter != "-" else{
+                continue
+            }
+            
+            if n == 0{
+                result.insert("-", at: 0)
+                n = K
+            }
+            
+            result.insert(aCharacter, at: 0)
+            n -= 1
+        }
+        
+        return String(result)
+    }
+}