归档 2015年7月

题目描述：

Implement the following operations of a queue using stacks.

• push(x) -- Push element x to the back of queue.
• pop() -- Removes the element from in front of queue.
• peek() -- Get the front element.
• empty() -- Return whether the queue is ...

题目描述：

Given an integer, write a function to determine if it is a power of two.

题目大意：

给定一个整数，编写函数判断它是否是2的幂。

解题思路：

如果一个整数是2的幂，那么它的二进制形式最高位为1，其余各位为0

等价于：n & (n - 1) = 0，且n > 0

Python代码：

class Solution:
    # @param {integer} n
    # @return {boolean ...

题目描述：

Given a binary search tree, write a function kthSmallest to find the kth smallest element in it.

Note: 

You may assume k is always valid, 1 ≤ k ≤ BST's total elements.

Follow up:

What if the BST ...