Added 'Valid Anagram'

Author: anthonyzhub

Valid Anagram.java

@@ -0,0 +1,46 @@
+// https://leetcode.com/problems/valid-anagram/
+
+class Solution {
+
+    private void strToMap(String s, Map<Character, Integer> sMap) {
+
+        for (char c: s.toCharArray()) {
+
+            Character ch = Character.valueOf(c);
+
+            if (sMap.containsKey(ch)) {
+                sMap.put(c, sMap.get(ch) + 1);
+            }
+            else {
+                sMap.put(ch, 1);
+            }
+        }
+    }
+
+    public boolean isAnagram(String s, String t) {
+
+        /*
+         * Time Complexity: O(n) where n = max(s.length, t.length). strToMap() will iterate both strings
+         *  and will take more time on the longest string.
+         * 
+         * Space Complexity: O(n + a) where n = max(s.length, t.length) and a = the size of the largest hash map.
+         *  E.g., if S is 26 characters long and has unique letters, then the charArray() and Map will hold 26 elements.
+         *  If S is 26 characters long and has 1 unique letter, then the char array will hold 26 letters while the map
+         *  has 1 element.
+         */
+        
+        if ((s.isEmpty() && !t.isEmpty()) || (!s.isEmpty() && t.isEmpty())) {
+            return false;
+        }
+
+        // Create 2 maps
+        Map<Character, Integer> sMap = new HashMap<>();
+        Map<Character, Integer> tMap = new HashMap<>();
+
+        // Store string in map
+        strToMap(s, sMap);
+        strToMap(t, tMap);
+
+        return sMap.equals(tMap);
+    }
+}