题目描述：
Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n.
For example:
Given n = 13,
Return 6, because digit 1 occurred in the following numbers: 1, 10 ...
归档 2015
[LeetCode]Number of Digit One
[LeetCode]Implement Queue using Stacks
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LeetCode.
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 ...
[LeetCode]Power of Two
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LeetCode.
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 ...
[LeetCode]Kth Smallest Element in a BST
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LeetCode.
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 ...
[LeetCode]Majority Element II
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LeetCode.
题目描述：
Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. The algorithm should run in linear time and in O(1) space.
Hint:
How many majority elements could it possibly ...