Add solution 811

Author: vulgur

Diff for: 811_SubdomainVisitCount.swift

@@ -0,0 +1,27 @@
+class Solution {
+    func subdomainVisits(_ cpdomains: [String]) -> [String] {
+        var dict = [String: Int]()
+        for item in cpdomains {
+            let pair = item.split(separator: " ")
+            let (count, domain) = (Int(pair[0])!, String(pair[1]))
+            let subdomains = getSubdomains(of: domain)
+            for sub in subdomains {
+                dict[sub] = (dict[sub] ?? 0) + count
+            }
+        }
+        return dict.map{item in "\(item.value) \(item.key)"
+        }
+    }
+    
+    func getSubdomains(of domain: String) -> [String] {
+        var subdomains = [String]()
+        var subdomain = domain
+        subdomains.append(subdomain)
+        while let i = subdomain.index(of: ".") {
+            subdomain = String(subdomain[subdomain.index(after:i)...])
+            subdomains.append(subdomain)
+            
+        }
+        return subdomains
+    }
+}