The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Given a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus sum of all keys greater than the original key in BST.

Given a Binary Search Tree and a target number, return true if there exist two elements in the BST such that their sum is equal to the given target. Example 1:

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

On a staircase, the i-th step has some non-negative cost cost[i] assigned (0 indexed).

Say you have an array for which the ith element is the price of a given stock on day i.If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit. Note that you cannot sell a stock before you buy one.