Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

Given a set of distinct integers, nums, return all possible subsets (the power set).

Write a program that outputs the string representation of numbers from 1 to n. But for multiples of three it should output “Fizz” instead of the number and for the multiples of five output “Buzz”. For numbers which are multiples of both three and five output “FizzBuzz”.

Write a function that reverses a string. The input string is given as an array of characters char[]. Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory. You may assume all the characters consist of printable ascii characters.

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.