## Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

## Integer Square Root, sqrt(x)

Implement square root function, `sqrt(x)`, that returns an integer result. The algorithm should run in O(log x).

## Hash Function

In data structure Hash, hash function is used to convert a string(or any other type) into an integer smaller than hash size and bigger or equal to zero. The objective of designing a hash function is to “hash” the key as unreasonable as possible. A good hash function can avoid collision as less as possible. A widely used hash function algorithm is using a magic number 33, consider any string as a 33 based big integer like follow:

## Climbing Stairs

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

## O(1) Check Power of 2

Using O(1) time to check whether an integer n is a power of 2.

## Unique Characters

Implement an algorithm to determine if a string has all unique characters.

## Two Strings Are Anagrams

Write a method `anagram(s,t)` to decide if two strings are anagrams. Two strings are anagrams if they have the same letters in different order.

## Remove Element

Given an array and a value, remove all occurrences of that value in place and return the new length.

## Nth to Last Node in List

Find the nth to last element of a singly linked list.

## Merge Two Sorted Lists

Merge two sorted (ascending) linked lists and return it as a new sorted list. The new sorted list should be made by splicing together the nodes of the two lists and sorted in ascending order.