Factorial digits sum
zero number of factorial
BlockingQueue
fixed
Longest common suffix
Remove duplicate
abc123 <=> a1b2c3
a b cde "f g""h j" => [a, b, cde, 'f g', 'h j’]
longest common suffix
valid utf-8
print tree based on set of pair
find path of given word
search in 2d array II
compressor string
Add implementation of trie
Random Set Structure
serialize and deserialize binary tree
以1/(2^n)的概率返回1，其它的时候返回0，题目应该假设有个函数可以生成1或者0，以1/2的概率