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Hello World!

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class MinimumDepthBinaryTreeBFS {
    public int minDepth(TreeNode root) {
        if(root == null) {
            return 0;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        int level = 0;
        while(!queue.isEmpty()) {
            level++;

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class MinimumDepthBinaryTreeDFS {
    public int minDepth(TreeNode root) {
        if(root == null) {
            return 0;
        }
        int leftHeight = minDepth(root.left);
        int rightHeight = minDepth(root.right);
        if(leftHeight == 0 || rightHeight == 0) {
            return leftHeight + rightHeight + 1;
        }

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class RomanToInteger {
    public int romanToInt(String s) {
        int prev = 0;
        int result = 0;
        for(int i = s.length() -1; i >= 0; i--) {
            char cur = s.charAt(i);
            int curVal = getInteger(cur);
            if(curVal < prev) {
                result -= curVal;
            } else {

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class ArrangingCoinsBS {
    public int arrangeCoins(int n) {
        int low = 1; 
        int high = n;
        while(low < high) {
            int mid = low +(high -low+1)/2;
            long num = (((long)mid * ((long)mid +1l))/2l);
            if(num == n) {
                return mid;
            } else if(n < num){

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class ArrangingCoins {
    public int arrangeCoins(int n) {
        double result = (-1.0 + Math.sqrt(1.0+8.0*n))/2.0;
        return (int)Math.floor(result);
    }
}

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class SubarrayProductLessThanK {
    public int numSubarrayProductLessThanK(int[] nums, int k) {
        if(k <= 1) {
            return 0;
        }
        int count = 0;
        int prod = 1;
        for(int i =0, j =0; j < nums.length; j++) {
            prod *= nums[j];
            while(prod >= k) {

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class SearchInRotatedArray {
    public int search(int[] nums, int target) {
        return search(nums, 0, nums.length - 1, target);
    }

    private int search(int[] nums, int start, int end, int target) {
        if (start > end) return -1;
        int midIdx = start + (end - start) / 2;
        int mid = nums[midIdx];
        if (target == mid) return midIdx;

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class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map<Integer, Integer> map = new HashMap<>();
        for(int i = 0; i < nums.length; i++) {
            int num = nums[i];
            if(map.containsKey(num)) {
                return new int[]{i, map.get(num)};
            } else {
                map.put(target - num, i);
            }

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public class BullsAndCows {
    public String getHint(String secret, String guess) {
        int n = secret.length();
        int[] map = new int[10];
        int a = 0;
        int b = 0;
        for (int i = 0; i < n; i++) {
            int s = secret.charAt(i) - '0';
            int g = guess.charAt(i) - '0';
            if (s == g) {