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题目： Invert a binary tree. to Trivia:This problem was inspired by this original tweet by Max Howell: 链接： http://leetcode.com/problems/invert-binary-tre 阅读全文
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题目: 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 阅读全文
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题目：Implement a basic calculator to evaluate a simple expression string.The expression string may contain open(and closing parentheses), the plus+or mi... 阅读全文
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题目： Find the total area covered by two rectilinear rectangles in a 2D plane. Each rectangle is defined by its bottom left corner and top right corner 阅读全文
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题目： Given a complete binary tree, count the number of nodes. Definition of a complete binary tree from Wikipedia:In a complete binary tree every level 阅读全文