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public class Solution {
    public String mirroring(String s) {
        String x = s.substring(0, (s.length()) / 2);
        return x + (s.length() % 2 == 1 ? s.charAt(s.length() / 2) : "") + new StringBuilder(x).reverse().toString();
    }
    public String nearestPalindromic(String n) {
        if (n.equals("1"))
            return "0";

        String a = mirroring(n);

cixuuz

public class Solution {
    public int findMinMoves(int[] machines) {
        int total = 0; 
        for(int i: machines) 
            total += i;
        if(total%machines.length != 0) 
            return -1;
        int avg = total/machines.length, cnt = 0, max = 0;
        
        for(int load: machines){

cixuuz

class Solution {
  // O(9^n) O(1)
    public char[][] updateBoard(char[][] board, int[] click) {
        int m = board.length;
        int n = board[0].length;
        
        if (click.length < 2) return board;
        int i = click[0];
        int j = click[1];
        

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class Solution {
  // O(n^2) O(n^2)
    public int countSubstrings(String s) {
        int n = s.length();
        
        int[][] dp = new int[n][n];
        int res = 0;
        
        for (int i = n - 1; i >= 0; i--) {
            dp[i][i] = 1;

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class Solution {
  // O(2^n) O(n)
    public int longestPalindromeSubseq(String s) {
        return helper(0, s.length()-1, s);    
    }
    
    private int helper(int left, int right, String s) {
        if (left == right) return 1;
        if (left > right) return 0;
        return s.charAt(left) == s.charAt(right) ? 2 + helper(left+1, right-1, s) :

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class Solution {
  // O(n) O(n)
    public int[] findFrequentTreeSum(TreeNode root) {
        HashMap<Integer, Integer> sums = new HashMap<Integer, Integer>();
        
        dfs(root, sums);
        
        List<Integer> res = new ArrayList<Integer>();
        int max = 0;
        

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class Solution {
  // O(n) O(n)
    public int findPairs(int[] nums, int k) {
        if (nums.length < 2 || k < 0) return 0;
        
        HashSet visited = new HashSet();
        HashSet pairs = new HashSet();
        
        for (int n : nums) {
            if (visited.contains(n+k)) {

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public class Solution {
    
    class Result {  // (size, rangeLower, rangeUpper) -- size of current tree, range of current tree [rangeLower, rangeUpper]
        int size;
        int lower;
        int upper;
        
        Result(int size, int lower, int upper) {
            this.size = size;
            this.lower = lower;

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class Solution {
  // O(n) o(h)
    private int max = 0;
    public int longestConsecutive(TreeNode root) {
        if (root == null) return 0;
        
        dfs(root, 0, root.val);
        return max;
    }
    

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// O(n) O(1) 
class Solution {
    public TreeNode inorderSuccessor(TreeNode root, TreeNode p) {
        if (root == null) return null;
        
        TreeNode succ = null;
        Deque<TreeNode> stack = new LinkedList<TreeNode>();
        
        while (!stack.isEmpty() || root != null) {
            if (root != null) {