Date : 21-04-30
[Theory of Computation Homework] Hacker's message
Author : Admin
Views : 334
Hi, this is hacker.
I hacked CCS homepage and I found your personal information.
In this post, I attached a text file that contains your SNS links. Haha.
Other information like Email address, IP address and credit card number is in somewhere in my hidden drive!
Catch me if you can ;)

[Problem 1] SNS link classifier

### Mission:
*Extract only valid **SNS links** from the text file.*

### (1) SNS link
- **Condition**
- **Form:** A..A://www.B..B.com/C..C
- **A..A** : Protocol (http, https)
- **B..B** : Name of Site (cyworld, facebook, instagram, twitter)
- **C..C** : User ID (any length of alphabets)
- Both uppercase and lowercase are allowed (e.g. hTTpS, TWittEr)

### (2) I/O Example
input.txt
https://www.facebook.com/heejo
https://www.faceb00k.com/heejo
http://www.cyworld.com/hyunji
hTTPs://WwW.TWiTter.COm/tjLEE

output.txt
https://www.facebook.com/heejo
http://www.cyworld.com/hyunji
hTTPs://WwW.TWiTter.COm/tjLEE

### Form of the password for the drive : ABCD
- A : a number of valid cyworld links
- B : a number of valid facebook links
- C : a number of valid instagram links
- D : a number of valid twitter links

Hacker's Hidden Drive
(Problem 2 and 3 are in the hidden drive!)