题目概述

原题链接

Median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value. So the median is the mean of the two middle value.

Examples: 
 `[2,3,4]` , the median is 3

 `[2,3]`, the median is (2 + 3) / 2 = 2.5

Design a data structure that supports the following two operations:

- void addNum(int num) - Add a integer number from the data stream to the data structure. 
- double findMedian() - Return the median of all elements so far.   
For example:

addNum(1)
addNum(2)
findMedian() -> 1.5
addNum(3) 
findMedian() -> 2

python虚拟环境

从python3.5开始,使用venv创建虚拟环境已经成为官方推荐的方案。 查看官方文档，可以看到如果想要创建一个干净的虚拟环境。方式如下

python -m venv myenv

Cython

Cython不是CPython的简称，而是一种提升Python代码执行效率的解决方案。 据说一般达到30x。一会我们来看看是不是真的。这个技术对老鸟来说已经是好多 年前的了。但是很多情况下python用户真的用不上，所以不知道也无妨。

题目概述

原题链接

Given an integer array nums, return the number of range sums that lie in [lower, upper] inclusive.
Range sum S(i, j) is defined as the sum of the elements in nums between indices i and j (i ≤ j), inclusive.

Example:
Given nums = [-2, 5, -1], lower = -2, upper = 2,
Return 3.
The three ranges are : [0, 0], [2, 2], [0, 2] and their respective sums are: -2, -1, 2.

题目概述

原题链接

You are given an integer array nums and you
have to return a new counts array. 
The counts array has the property where counts[i] is 
the number of smaller elements to the right of nums[i].

Example:

Given nums = [5, 2, 6, 1]

To the right of 5 there are 2 smaller elements (2 and 1).
To the right of 2 there is only 1 smaller element (1).
To the right of 6 there is 1 smaller element (1).
To the right of 1 there is 0 smaller element.
Return the array [2, 1, 1, 0].

问题

以下Python代码实现对Excel转存的csv文件进行读取。

1
2

import pandas as pd
df = pd.read_csv(file_path + file_name + ".csv", encoding="gbk")

问题

同事写R程序的时候，问我能不能获取一个变量的name， 我说这个好办啊，在R里可以这样写，用quote()

> a <- 1
> quote(a)
a

不过我把问题想简单了，他实际需要的是要获得传入 参数的name。例如定义一个函数foo(c), 给它传入参数a，我能够在函数 内部知道传入参数的名字a。

题目概述

原题链接

Given a string that contains only digits 0-9 and a target value, return all possibilities to add binary operators (
not unary) +, -, or * between the digits so they evaluate to the target value.

 "123", 6 -> ["1+2+3", "1*2*3"] 
 "232", 8 -> ["2*3+2", "2+3*2"]
 "105", 5 -> ["1*0+5","10-5"]
 "00", 0 -> ["0+0", "0-0", "0*0"]
 "3456237490", 9191 -> []

题目概述

224原题链接

227原题链接

Implement a basic calculator to evaluate a simple expression string.

这两道题可以使用一种通用的解法来解。所以就放在一起了。

"1 + 1" = 2
" 2-1 + 2 " = 3
"(1+(4+5+2)-3)+(6+8)" = 23

"3+2*2" = 7
" 3/2 " = 1
" 3+5 / 2 " = 5

题目概述

原题链接

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.

Example 1:

11110
11010
11000
00000
Answer: 1

Example 2:

11000
11000
00100
00011
Answer: 3