Udemy: Data structure in Python lesson 1,2 :O(n)

1 Introduction

【Udemy高分付费课程】Python数据结构与算法 - 终极 Python 编码面试和计算机科学训练营（中英文字幕）_哔哩哔哩_bilibili断断续续一周刷完了udemy的数据结构和算法课程，由于之前只学过Python和Matlab，所以选择用python来学习数据结构；视频通过动画演示，使晦涩难懂的知识变得清晰有趣了很多，以此作为入门是极好的（尤其是英语不错的同学），推荐一波。

2 Big O

​​​​​​​Big O is the compare effect for both the time complexity and space complexity. It describes the worst case when running a program, which leads to the biggest complexity.

omega (n): best case, theta(n): medium case, O(n): worst case

2.1 O(n)

Some examples:

O(n) : proportional

O(n*2): loop within a loop

O(log n): divide and conquer

O(1): constant

O(n log n):  a combined case o