Given an array of integers `nums` and an integer `target`, return indices of the two numbers such that they add up to `target`. You may assume that each input would have exactly one solution, and you may not use the same element twice. You can return the answer in any order.

Given a string `s` containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: open brackets must be closed by the same type of brackets, and open brackets must be closed in the correct order. Every close bracket has a corresponding open bracket of the same type.

You are given an array `prices` where `prices[i]` is the price of a given stock on the ith day. You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock. Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.

Given the `root` of a binary tree, return the inorder traversal of its nodes' values. In an inorder traversal, you visit the left subtree first, then the current node, then the right subtree.

You are climbing a staircase. It takes `n` steps to reach the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?