solves #266: solves Palindrome number in java

Author: anishLearnsToCode

README.md

@@ -232,7 +232,7 @@
 | 261  | 🔒 [Graph Valid Tree](https://leetcode.com/problems/graph-valid-tree)                                                                                                  |                                                                                       [![Java](assets/java.png)](src/GraphValidTree.java)                                                                                        |                                                                                                                                   |
 | 263  | [Ugly Number](https://leetcode.com/problems/ugly-number)                                                                                                               |                                                              [![Java](assets/java.png)](src/UglyNumber.java) [![Python](assets/python.png)](python/ugly_number.py)                                                               |                                                                                                                                   |
 | 264  | [Ugly Number II](https://leetcode.com/problems/ugly-number-ii)                                                                                                         |                                                                                        [![Java](assets/java.png)](src/UglyNumberII.java)                                                                                         |                                                                                                                                   |
-| 266  | 🔒 [Palindrome Permutation](https://leetcode.com/problems/palindrome-permutation)                                                                                      |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 266  | 🔒 [Palindrome Permutation](https://leetcode.com/problems/palindrome-permutation)                                                                                      |                                                                                    [![Java](assets/java.png)](src/PalindromePermutation.java)                                                                                    |                                                                                                                                   |
 | 267  | 🔒 [Palindrome Permutation II](https://leetcode.com/problems/palindrome-permutation-ii)                                                                                |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 268  | [Missing Number](https://leetcode.com/problems/missing-number)                                                                                                         |                                                           [![Java](assets/java.png)](src/MissingNumber.java) [![Python](assets/python.png)](python/missing_number.py)                                                            |                                                                                                                                   |
 | 269  | [Alien Dictionary](https://leetcode.com/problems/alien-dictionary)                                                                                                     |                                                                                       [![Java](assets/java.png)](src/AlienDictionary.java)                                                                                       |                                                                                                                                   |

src/PalindromePermutation.java

@@ -0,0 +1,32 @@
+// https://leetcode.com/problems/palindrome-permutation
+// T: O(|s|)
+// S: O(|s|)
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class PalindromePermutation {
+    public boolean canPermutePalindrome(String s) {
+        final Map<Character, Integer> frequencies = getCharacterFrequencies(s);
+        return getNumberOfOddChars(frequencies) <= 1;
+    }
+
+    private static Map<Character, Integer> getCharacterFrequencies(String string) {
+        final Map<Character, Integer> result = new HashMap<>();
+        for (int i = 0 ; i < string.length() ; i++) {
+            final char c = string.charAt(i);
+            result.put(c, result.getOrDefault(c, 0) + 1);
+        }
+        return result;
+    }
+
+    private static int getNumberOfOddChars(Map<Character, Integer> frequencies) {
+        int result = 0;
+        for (int freq : frequencies.values()) {
+            if (freq % 2 == 1) {
+                result++;
+            }
+        }
+        return result;
+    }
+}