Add a solution to First Unique Character in a String

soapyigu · soapyigu · commit eca6d962ab95 · 2017-04-08T14:50:09.000-07:00
diff --git a/README.md b/README.md
@@ -27,7 +27,7 @@
 * [Microsoft](#microsoft)
 
 ## Progress
-[Problem Status](#problem-status) shows the latest progress to all 500+ questions. Currently we have 218 completed solutions. Note: questions with &hearts; mark means that you have to **Subscript to premium membership** of LeetCode to unlock them. Thank you for great contributions from [CharleneJiang](https://github.com/CharleneJiang), [ReadmeCritic](https://github.com/ReadmeCritic), [demonkoo](https://github.com/demonkoo), [DaiYue](https://github.com/DaiYue), [Quaggie](https://github.com/Quaggie) and [jindulys](https://github.com/jindulys).
+[Problem Status](#problem-status) shows the latest progress to all 500+ questions. Currently we have 219 completed solutions. Note: questions with &hearts; mark means that you have to **Subscript to premium membership** of LeetCode to unlock them. Thank you for great contributions from [CharleneJiang](https://github.com/CharleneJiang), [ReadmeCritic](https://github.com/ReadmeCritic), [demonkoo](https://github.com/demonkoo), [DaiYue](https://github.com/DaiYue), [Quaggie](https://github.com/Quaggie) and [jindulys](https://github.com/jindulys).
 
 
 ## Array
@@ -73,6 +73,7 @@
 | Title | Solution | Difficulty | Time | Space |
 | ----- | -------- | ---------- | ---- | ----- |
 [Fizz Buzz](https://leetcode.com/problems/fizz-buzz/)| [Swift](./FizzBuzz.swift)| Easy| O(n)| O(1)|
+[First Unique Character in a String](https://leetcode.com/problems/first-unique-character-in-a-string/)| [Swift](./FirstUniqueCharacterInString.swift)| Easy| O(n)| O(1)|
 [Keyboard Row](https://leetcode.com/problems/keyboard-row/)| [Swift](./KeyboardRow.swift)| Easy| O(nm)| O(n)|
 [Valid Palindrome](https://leetcode.com/problems/valid-palindrome/)| [Swift](./String/ValidPalindrome.swift)| Easy| O(n)| O(n)|
 [Detect Capital](https://leetcode.com/problems/detect-capital/)| [Swift](./String/DetectCapital.swift)| Easy| O(n)| O(1)|
diff --git a/String/FirstUniqueCharacterInString.swift b/String/FirstUniqueCharacterInString.swift
@@ -0,0 +1,31 @@
+/**
+ * Question Link: https://leetcode.com/problems/first-unique-character-in-a-string/
+ * Primary idea: Keep track of existence of each character in the string
+ * 
+ * Note: The maximum space of the dictionary is 26, so space complexity is O(1)
+ *
+ * Time Complexity: O(n), Space Complexity: O(1)
+ *
+ */
+
+class FirstUniqueCharacterInString {
+    func firstUniqChar(_ s: String) -> Int {
+        var dict = [Character: Bool]()
+        
+        for char in s.characters {
+            if let isDup = dict[char] {
+                dict[char] = true
+            } else {
+                dict[char] = false
+            }
+        }
+        
+        for (i, char) in Array(s.characters).enumerated() {
+            if !dict[char]! {
+                return i
+            }
+        }
+        
+        return -1
+    }
+}
