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Insert Delete getRandom O(1)

Design and implement an efficient sampler that works in average O(1) time complexity.

Binary Tree Upside Down

Given a binary tree where every node has either 0 or 2 children and every right node is a leaf node, flip it upside down turning it into a binary tree where all left nodes are leaf nodes.

Find Leaves of a Binary Tree

Given a binary tree, extract all the leaves in repeated succession into a list of lists by starting at the bottom and working your way upwards.

K Largest Elements

Write an efficient program for printing k largest elements in an array. Largest elements are returned in order largest to smallest.

Generate Parentheses

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

Shuffle String

Write a function that takes a string as an input and returns a shuffled version of that string then write another function to analyze how well it was shuffled.