Given an array of integers, every element appears twice except for one. Find that single one.
Note:
Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?

Implement int sqrt(int x).
Compute and return the square root of x.
x is guaranteed to be a non-negative integer.

Given an input string, reverse the string word by word.

For example,
Given s = "the sky is blue",
return "blue is sky the".

Could you do it in-place without allocating extra space?

Well, hope I can find a job.