solves #3158: Find the XOR of Numbers Which Appear Twice

Author: anishLearnsToCode

README.md

@@ -912,7 +912,7 @@
 | 3142 | [Check if Grid Satisfies Conditions](https://leetcode.com/problems/check-if-grid-satisfies-conditions)                                                                 |                                                                               [![Java](assets/java.png)](src/CheckIfGridSatisfiesConditions.java)                                                                                |                                                                                                                                   |
 | 3146 | [Permutation Difference between Two Strings](https://leetcode.com/problems/permutation-difference-between-two-strings)                                                 |                                                                           [![Java](assets/java.png)](src/PermutationDifferenceBetweenTwoStrings.java)                                                                            |                                                                                                                                   |
 | 3151 | [Special Array I](https://leetcode.com/problems/special-array-i)                                                                                                       |                                                                                        [![Java](assets/java.png)](src/SpecialArrayI.java)                                                                                        |                                                                                                                                   |
-| 3158 | [Find the XOR of Numbers Which Appear Twice](https://leetcode.com/problems/find-the-xor-of-numbers-which-appear-twice)                                                 |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 3158 | [Find the XOR of Numbers Which Appear Twice](https://leetcode.com/problems/find-the-xor-of-numbers-which-appear-twice)                                                 |                                                                             [![Java](assets/java.png)](src/FindTheXOROfNumbersWhichAppearTwice.java)                                                                             |                                                                                                                                   |
 | 3162 | [Find the Number of Good Pairs I](https://leetcode.com/problems/find-the-number-of-good-pairs-i)                                                                       |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 3168 | [Minimum Number of Chairs in a Waiting Room](https://leetcode.com/problems/minimum-number-of-chairs-in-a-waiting-room)                                                 |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 3173 | [Bitwise OR of Adjacent Elements](https://leetcode.com/problems/bitwise-or-of-adjacent-elements)                                                                       |                                                                                                                                                                                                                                  |                                                                                                                                   |

src/FindTheXOROfNumbersWhichAppearTwice.java

@@ -0,0 +1,20 @@
+// https://leetcode.com/problems/find-the-xor-of-numbers-which-appear-twice
+// T: O(N)
+// S: O(N)
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class FindTheXOROfNumbersWhichAppearTwice {
+    public int duplicateNumbersXOR(int[] array) {
+        final Set<Integer> numbers = new HashSet<>();
+        int result = 0;
+        for (int element : array) {
+            if (numbers.contains(element)) {
+                result ^= element;
+            }
+            numbers.add(element);
+        }
+        return result;
+    }
+}