RakhmedovRS

    public boolean isValidBST(TreeNode root)
    {
        Integer[] prev = new Integer[1];
        return isValidBST(root, prev);
    }

    public boolean isValidBST(TreeNode root, Integer[] prev)
    {
        boolean left = true;
        if (root.left != null)

RakhmedovRS

	public int[] topKFrequent(int[] nums, int k) {
		Map<Integer, Integer> valueToCount = new HashMap<>();
		int max = 0;
		for (int num : nums) {
			int count = valueToCount.getOrDefault(num, 0) + 1;
			valueToCount.put(num, count);
			max = Math.max(max, count);
		}

		System.out.println(valueToCount);

RakhmedovRS

		int pos = max;
		int[] answer = new int[k];
		int i = 0;
		while (pos >= 0) {
			for (int value : buckets.get(pos)) {
				answer[i++] = value;
				if (i == k) {
					return answer;
				}
			}

RakhmedovRS

		for (Map.Entry<Integer, Integer> entry : valueToCount.entrySet()) {
			buckets.get(entry.getValue()).add(entry.getKey());
		}

RakhmedovRS

		List<List<Integer>> buckets = new ArrayList<>();
		for (int i = 0; i <= max; i++) {
			buckets.add(new ArrayList<>());
		}

RakhmedovRS

		Map<Integer, Integer> valueToCount = new HashMap<>();
		int max = 0;
		for (int num : nums) {
			int count = valueToCount.getOrDefault(num, 0) + 1;
			valueToCount.put(num, count);
			max = Math.max(max, count);
		}

RakhmedovRS

	public int[] topKFrequent(int[] nums, int k) {
		Map<Integer, Integer> valueToCount = new HashMap<>();
		for (int num : nums) {
			int count = valueToCount.getOrDefault(num, 0) + 1;
			valueToCount.put(num, count);
		}

		int pos = 0;
		int[] answer = new int[k];
		PriorityQueue<Integer> pq = new PriorityQueue<>((a,b) ->

RakhmedovRS

		int pos = 0;
		int[] answer = new int[k];
		PriorityQueue<Integer> pq = new PriorityQueue<>((a,b) -> 
				valueToCount.get(b) - valueToCount.get(a));
		pq.addAll(valueToCount.keySet());
		while (k-- > 0)
		{
			answer[pos++] = pq.remove();
		}

RakhmedovRS

PriorityQueue<Integer> pq = new PriorityQueue<>((a,b) -> 
  valueToCount.get(b) - valueToCount.get(a));

RakhmedovRS

        Map<Integer, Integer> valueToCount = new HashMap<>();
        for (int num : nums) {
            int count = valueToCount.getOrDefault(num, 0) + 1;
            valueToCount.put(num, count);
        }