题目描述：

Given a linked list, determine if it has a cycle in it.

Can you solve it without using extra space?

解题思路：

fast指针每次向前运动两个节点，slow指针每次向前运动一个节点

Python代码（快慢指针）：

# Definition for singly-linked list ...

题目描述：

Given a sorted integer array without duplicates, return the summary of its ranges.

For example, given [0,1,2,4,5,7], return ["0->2","4->5","7"].

浮点精度问题简析 作者是 在线疯狂 发布于 2015年6月24日 在 译林.

Why don’t my numbers add up?

So you’ve written some absurdly simple code, say for example:

0.1 + 0.2

and got a really unexpected result:

0.30000000000000004

Why don’t my numbers, like 0 ...

题目描述：

Implement a basic calculator to evaluate a simple expression string.

The expression string contains only non-negative integers, +, -, *, / operators and empty spaces . The integer division should truncate toward zero.

You may assume that the given expression is always valid.

Some ...

题目描述：

Invert a binary tree.

4
/   \
2     7
/ \    / \
1   3   6  9

to

4
/   \
7     2
/ \   / \
9   6  3  1

Trivia:

This problem was inspired by this original tweet by Max Howell:

Google: 90% of our engineers use the software ...