Cesarcmv

class Solution {
    public int[] singleNumber(int[] nums) {
        Set<Integer> set = new HashSet<>();
        for(Integer i: nums){
            if(!set.add(i)){
                set.remove(i);
            }
        }
        
        int j = 0;

Cesarcmv

class Solution {
    
    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
        List<List<Integer>> finalList = new ArrayList();

        if(root == null){
            return finalList;
        }
        
        List<TreeNode> list = new ArrayList<>();        

Cesarcmv

class Solution {
    public ListNode removeElements(ListNode head, int val) {
      if (head != null) {
            ListNode prev = null;
            ListNode node = head;
            while (node != null) {
               if (node.val == val) {
                   if (prev == null) {
                       head = node.next;
                   } else {

Cesarcmv

class Solution {

    public int[] topKFrequent(int[] nums, int k) {
        
        if (k == nums.length) {
            return nums;
        }
        
        Map<Integer, Integer> count = new HashMap();
        for (int n: nums) {

Cesarcmv

class Solution {
    
    public double myPow(double x, int n) {
        double ans = 1;
        if(n<0){
            x = 1/x;
        }
        while(n!=0){
            if(n%2!=0){
                ans *= x;

Cesarcmv

class Solution {
    public String reverseWords(String s) {
        List<String> list = Arrays.asList(s.split(" "))
                .stream()
                .filter(s1 -> !s1.isEmpty())
                .collect(Collectors.toList());
        
        if (list.size() == 0) {
            return s.trim();
        }

Cesarcmv

public class Solution {
    // you need treat n as an unsigned value
    public int reverseBits(int n) {
        int ans = 0;
        for (int i = 0; i < 32; i++) {
            ans <<= 1;
            ans = ans | (n & 1);
            n >>= 1;
        }
        return ans;

Cesarcmv

public List<List<Integer>> subsets(int[] nums) {
        List<List<Integer>> result = new ArrayList();
        result.add(new ArrayList<>());
        for (int num : nums) {
            List<List<Integer>> subList = new ArrayList();
            for (List<Integer> current : result) {
                List list = new ArrayList<>(current);
                list.add(num);
                subList.add(list);
            }

Cesarcmv

public List<List<Integer>> threeSum(int[] nums) {
        Map<Integer, Set<Integer>> map = new HashMap();
        List<List<Integer>> threeSumList = new ArrayList();
        Set<Map<Integer, Integer>> threeSumSet = new HashSet<>();

        for (int i = 0; i < nums.length; i++) {
            putOnMap(i, nums[i], map);
        }

        for (int j = 0; j < nums.length; j++) {

Cesarcmv

class Solution {
    public int islandPerimeter(int[][] grid) {
        int p = 0;
        for(int j=0; j<grid.length; j++){
            for(int i=0; i<grid[0].length; i++){
                if(grid[j][i] == 1){
                    p += dfs(j,i,grid);    
                }
            }
        }