n objects colored red, white or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white and blue.
Find all nodes at k distance from leaf nodes
Reverse a linked list
Given a binary tree, calculate the frequency of sub-tree sum.
Design a stack that pops most frequent value
Simplify unix file path
Merge two sorted array in place
Nested list weight sum
Second last item in linked list
Count number of set bits
Next bigger permutation for a number
Given an array and target k find all sub-array with sum k
Reverse all words, keeping punctuations
Depth of binary tree without recursion
Longest common sequence