Merge branch 'master' of https://github.com/jianminchen/Leetcode_C-

Author: jianminchen

2017 July -/Leetcode 387 First unique Character in a string.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Leetcode387_FirstUniqueCharacterInAString
+{
+    /// <summary>
+    /// Leetcode 387 - First unique character in a string
+    /// https://leetcode.com/problems/first-unique-character-in-a-string/description/
+    /// </summary>
+    class Program
+    {
+        static void Main(string[] args)
+        {
+        }
+        
+        public int FirstUniqChar(string s)
+        {
+            if (s == null || s.Length == 0)
+                return -1;
+
+            int SIZE = 26;
+            var count = new int[SIZE];
+            var length = s.Length;
+            for (int i = 0; i < length; i++)
+            {
+                count[s[i] - 'a']++;
+            }
+
+            // find first one with count = 1
+            var hashset = new HashSet<char>(s.ToCharArray());
+            for (int i = 0; i < length; i++)
+            {
+                var current = s[i];
+                if (hashset.Contains(current))
+                {
+                    if (count[current - 'a'] == 1)
+                        return i;
+
+                    hashset.Remove(current);
+                }
+            }
+
+            return -1;
+        }        
+    }
+}