[Array] Add a solution to Validate IP Address

Array/ValidateIPAddress.swift

@@ -0,0 +1,94 @@
+/**
+ * Question Link: https://leetcode.com/problems/validate-ip-address/
+ * Primary idea: Determine whether they are iPv4 or iPv6, then handle them separately
+ *
+ * Time Complexity: O(n), Space Complexity: O(1)
+ *
+ */
+
+class ValidateIPAddress {
+
+    let IPv4 = "IPv4"
+    let IPv4Separator = Character(".")
+    let IPv6 = "IPv6"
+    let IPv6Separator = Character(":")
+    let InvalidIP = "Neither"
+
+    func validIPAddress(_ IP: String) -> String {
+        // detect IPv4 or IPv6
+        guard let isIPv4 = isPotentialIPv4(IP) else {
+            return InvalidIP
+        }
+
+        return isIPv4 ? isValidIPv4(IP) : isValidIPv6(IP)
+    }
+
+    private func isPotentialIPv4(_ IP: String) -> Bool? {
+        let isIPv4 = IP.contains(IPv4Separator), isIPv6 = IP.contains(IPv6Separator)
+
+        if isIPv4 || isIPv6 {
+            return isIPv4
+        } else {
+            return nil
+        }
+    }
+
+    private func isValidIPv4(_ IP: String) -> String {
+        if IP.contains("\(IPv4Separator)\(IPv4Separator)") || IP.first == IPv4Separator || IP.last == IPv4Separator {
+            return InvalidIP
+        }
+
+        let numbers = IP.split(separator: IPv4Separator)
+
+        guard numbers.count == 4 else {
+            return InvalidIP
+        }
+
+        for number in numbers {
+            guard let num = Int(number) else {
+                return InvalidIP
+            }
+
+            guard let first = number.first, first.isNumber else {
+                return InvalidIP
+            }
+
+            if first == "0", number.count > 1 {
+                return InvalidIP
+            }
+            if num < 0 || num > 255 {
+                return InvalidIP
+            }
+        }
+
+        return IPv4
+    }
+
+    private func isValidIPv6(_ IP: String) -> String {
+        if IP.contains("\(IPv6Separator)\(IPv6Separator)") || IP.first == IPv6Separator || IP.last == IPv6Separator {
+            return InvalidIP
+        }
+
+        let numbers = IP.split(separator: IPv6Separator)
+
+        guard numbers.count == 8 else {
+            return InvalidIP
+        }
+
+        for number in numbers {
+            let number = number.lowercased()
+
+            if number.count > 4 {
+                return InvalidIP
+            }
+
+            for char in number {
+                if !char.isHexDigit {
+                    return InvalidIP
+                }
+            }
+        }
+
+        return IPv6
+    }
+}

README.md

@@ -4,7 +4,7 @@
 ![Leetcode](./logo.png?style=centerme)
 
 ## Progress
-[Problem Status](#problem-status) shows the latest progress to all 1000+ questions. Currently we have 322 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them.
+[Problem Status](#problem-status) shows the latest progress to all 1000+ questions. Currently we have 323 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them.
 
 ## Contributors
 
@@ -93,7 +93,7 @@
 [Gas Station](https://leetcode.com/problems/gas-station/)| [Swift](./Array/GasStation.swift)| Medium| O(n)| O(1)|
 [Game of Life](https://leetcode.com/problems/game-of-life/)| [Swift](./Array/GameLife.swift)| Medium| O(n)| O(1)|
 [Task Scheduler](https://leetcode.com/problems/task-scheduler/)| [Swift](./Array/TaskScheduler.swift)| Medium| O(nlogn)| O(n)|
-[]
+[Validate IP Address](https://leetcode.com/problems/validate-ip-address/)| [Swift](./Array/ValidateIPAddress.swift)| Medium| O(n)| O(1)|
 [Sliding Window Maximum ](https://leetcode.com/problems/sliding-window-maximum/)| [Swift](./Array/SlidingWindowMaximum.swift)| Hard| O(n)| O(n)|
 [Longest Consecutive Sequence](https://leetcode.com/problems/longest-consecutive-sequence/)| [Swift](./Array/LongestConsecutiveSequence.swift)| Hard| O(n)| O(n)|
 [Create Maximum Number](https://leetcode.com/problems/create-maximum-number/)| [Swift](./Array/CreateMaximumNumber.swift)| Hard| O(n^2)| O(n)|