档案日期2015的23

2015年6月8日 - 2015年6月14日

[LeetCode]Implement Stack using Queues

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 ...

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[LeetCode]Basic Calculator

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 ...

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