作者归档：在线疯狂

Why don’t my numbers add up?

为什么我的数加起来对不上？

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

你写了一段极其简单的代码，比如：

    0.1 + 0.2

and got a really unexpected result:

然后得到了一个意想不到的结果：

    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 ...

题目描述：

Implement the following operations of a stack using queues.

push(x) -- Push element x onto stack.
pop() -- Removes the element on top of the stack.
top() -- Get the top element.
empty() -- Return whether the stack is empty.

Notes:
You ...

题目描述：

Implement a basic calculator to evaluate a simple expression string.

The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers and empty spaces .

You may assume that the given expression is always valid ...