wushbin

class Solution {
    public boolean canTransform(String start, String end) {
        int pt1 = 0, pt2 = 0;
        
        int len1 = start.length();
        int len2 = end.length();
        
        while(pt1 < len1 || pt2 < len2) {
            // find not X
            while(pt1 < len1 && start.charAt(pt1) == 'X') {

wushbin

class Solution {
    public int maxRotateFunction(int[] A) {
        int sum = 0;
        int F = 0;
        int len = A.length;
        for (int i = 0; i < len; i++) {
            sum += A[i];
            F += i * A[i];
        }
        

wushbin

class Solution {
    Map<Integer, Integer> shuffle;
    int n;
    Random rand;
    int n_rows;
    int n_cols;
    public Solution(int n_rows, int n_cols) {
        this.n = n_rows * n_cols;
        this.shuffle = new HashMap<>();
        this.rand = new Random();

wushbin

class Solution {
    public int findNthDigit(int n) {
        long base = 1;
        int cnt = 1;// cnt -> number of digits
        
        while(n > 9 * base * cnt) {
            n -= (9 * base * cnt);
            cnt += 1;
            base *= 10;
        }

wushbin

class Solution {
    public boolean checkSubarraySum(int[] nums, int k) {
        Map<Integer, Integer> map = new HashMap<>();
        int sum = 0;
        map.put(0, -1);
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
            if (k != 0) {
                sum %= k;
            }

wushbin

class Solution {
    public int subarrayBitwiseORs(int[] A) {
        Set<Integer> result = new HashSet<>();
        Set<Integer> current = new HashSet<>();
        
        for (int num : A) {
            Set<Integer> temp = new HashSet<>();
            temp.add(num);
            for (int pre : current) {
                temp.add(num | pre);

wushbin

class Solution {
    public int rangeBitwiseAnd(int m, int n) {
        int i = 0;
        while(m != n) {
            m >>= 1;
            n >>= 1;
            i++;
        }
        return m << i;
    }

wushbin

class Solution {
    public int[] addNegabinary(int[] arr1, int[] arr2) {
        List<Integer> list = new ArrayList<>();
        
        int pt1 = arr1.length - 1;
        int pt2 = arr2.length - 1;
        
        int carrier = 0;
        
        while(pt1 >= 0 || pt2 >= 0) {

wushbin

class MajorityChecker {
    class SegmentTreeNode {
        int major;
        int freq;
        int start;
        int end;
        SegmentTreeNode left;
        SegmentTreeNode right;
        
        public SegmentTreeNode (int start, int end) {

wushbin

class Solution {
    class TrieNode {
        char c;
        String word;
        TrieNode[] children;
        boolean isWord;
        
        public TrieNode(char c) {
            this.c = c;
            this.children = new TrieNode[26];