Unique char in string: done

Author: rampatra

src/main/java/com/leetcode/strings/AnagramsInString.java

@@ -50,8 +50,10 @@ private static List<Integer> findAllAnagramsInTextNaive(String text, String patt
     }
 
     /**
-     * Time complexity: O(n). Completes within <a href="https://leetcode.com/submissions/detail/222911434/">7ms on
-     * leetcode.</a>
+     * Completes within <a href="https://leetcode.com/submissions/detail/222911434/">7ms on leetcode.</a>
+     * Time complexity: O(n)
+     * where,
+     * n = length of text or number of characters in text
      *
      * @param text
      * @param pattern

src/main/java/com/leetcode/strings/UniqueCharacterInString.java

@@ -0,0 +1,37 @@
+package com.leetcode.strings;
+
+/**
+ * Leetcode Problem: https://leetcode.com/problems/first-unique-character-in-a-string/
+ *
+ * @author rampatra
+ * @since 2019-04-16
+ */
+public class UniqueCharacterInString {
+
+    /**
+     * Completes within <a href="https://leetcode.com/submissions/detail/222914261/">7ms on leetcode.</a>
+     * Time complexity: O(n)
+     *
+     * @param str the input string
+     * @return the index of the first non-repeating character in {@code str}, {@code -1} otherwise.
+     */
+    private static int findFirstUniqueCharacterInString(String str) {
+        int[] charCount = new int[26];
+
+        for (int i = 0; i < str.length(); i++) {
+            charCount[str.charAt(i) - 'a']++;
+        }
+
+        for (int i = 0; i < str.length(); i++) {
+            if (charCount[str.charAt(i) - 'a'] == 1) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(findFirstUniqueCharacterInString("leetcode"));
+        System.out.println(findFirstUniqueCharacterInString("loveleetcode"));
+    }
+}