| 3168|[Minimum Number of Chairs in a Waiting Room](https://leetcode.com/problems/minimum-number-of-chairs-in-a-waiting-room/)|[Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3168.java)|| Easy|

| 3164|[Find the Number of Good Pairs II](https://leetcode.com/problems/find-the-number-of-good-pairs-ii/)|[Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3164.java)|| Medium|

| 3162|[Find the Number of Good Pairs I](https://leetcode.com/problems/find-the-number-of-good-pairs-i/)|[Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3162.java)|| Easy|

| 3158|[Find the XOR of Numbers Which Appear Twice](https://leetcode.com/problems/find-the-xor-of-numbers-which-appear-twice/)|[Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3158.java)|| Easy|

| 3157 |[Find the Level of Tree with Minimum Sum](https://leetcode.com/problems/find-the-level-of-tree-with-minimum-sum/) |[Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3157.java) | | Medium |BFS

| 3142|[Check if Grid Satisfies Conditions](https://leetcode.com/problems/check-if-grid-satisfies-conditions/)|[Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3142.java)|| Easy|

| 3131|[Find the Integer Added to Array I](https://leetcode.com/problems/find-the-integer-added-to-array-i/)|[Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3131.java)|| Easy|

packagecom.fishercoder.solutions.fourththousand;

importjava.util.HashSet;

importjava.util.Set;

publicclass_3158 {

publicstaticclassSolution1 {

publicintduplicateNumbersXOR(int[]nums) {

intans =0;

Set<Integer>met =newHashSet<>();

for (intnum :nums) {

if (!met.add(num)) {

ans ^=num;

}

}

returnans;

}

}

}