---
# System prepended metadata

title: 211211 Class Notes - Jack
tags: [Mathematics, Jack, Programming, BookMode, Tutor]

---

---
description: Algorithm class with Jack
image: https://hackmd.io/_uploads/BJj4o-z5Y.jpg
---
# 211211 Class Notes - Jack
###### tags: `Jack` `Tutor` `Programming` `Mathematics` `BookMode`

[TOC]

## LeetCode

### 13. Roman to Integer

![](https://hackmd.io/_uploads/BksvXzz5t.png)

- [x] 把每個位數分開來(a)
- [x] 判斷a是否大於4--------------1
- [x] (1)如果是,判斷是否等於九-----2
- [x] (2)如果是,打出相應符號
- [ ] (2)如果否,打出相應符號
- [ ] (1)如果否,判斷是否等於四-----3
- [ ] (3)如果是,打出相應符號
- [ ] (3)如果否,打出相應符號

## Notes

### List: Append
> Add new element to the list
```python=
a = [] # start an empty list
n = ['1', '2', '3', '4'] # read number of element in the list
for i in range(len(n)):  
    a.append(i[n]) # add it to the list
print(a)
```

### List: join
> join all the thing in list
```python=
a = [1, 2, 3]
print(' '.join([str(i) for i in a]))
```
