Name: Marcus Liu
Discord: sucram314.

M4 (Grade 10) Student at UTS

orz Pear hen Tangerine259 tofu andyloo666 goofygoober hxian laight sonje 4fecta Nils_Emmenegger bruce XTL Riolku NK Snowfall dxke02 El20082 NotDiamand likevrui Kevkev_yanrui

hen IOI when

WE DONE IT!!!!!!!!!!!

Thank you to everybody who participated in UTS Open '24!

Here is some commentary on the problemset:

Watering the Plants (5p)
hehehe trollolololo just because its my least favourite out of the ones i set or collabed on doesn't mean i don't like the problem, i think i did an okay job making a P1 that still requires some thinking :)

Happy Gifts (7p)
also kinda troll, made constrains big enough so dp doesn't work haha. fun fact i made an incorrect reference solution on this problem and Riolku was the first person to point it out... GG 😭

LXghts Out (10p)
AD HOC MOMENT !!!!! i like how final implementation is so tiny but to get there i need 99999% brainpower. fun fact i also made an incorrect reference solution for this problem because i thought you had to flip two at a time from the ends of odd sequences... even funner fact me and tofu originally tried to make this problem on a 2D GRID but that was way too hard... if somebody can generalize this problem to higher dimensions that would be so cool pls lmk

Political Espionage (12p)
cool construction, 4fecta orz, i legit was originally gonna make the problem counting # of pairs, which also has a divide and conquer ish solution interestingly 🤔, also it might've been wise to score solutions based on their max value instead of # of pairs..

Parity Challenge (17p)
look i know its ds spam but i think its an interesting trick to allow modification on values AND operations and even if thats a well known technique among pros im happy that i came up with this through experimentation on my own ˋ( ° ▽、° )

Candygrams (20p)
beautiful reduction to path sum and query, i don't care what the haters say about it being a boring HLD problem, tofu orz 🫡

Notes

tfw your top problems are either scuffed or math related
update: still kinda scuffed, but getting better hopefully

note to self: sometimes c++ tles not because ur algorithm is too slow, but because ur array bounds aren't correct (this happened way too many times) usually just add some extra cells to ur array and it will work

update: I now always add extra cells to my arrays :)

other common errors (trivial yet deadly):

• index off by 1
• swapped rows and columns of a grid
• bad io (especially if you use an unsigned scan macro on negative integers D:)
• wrong data type
• misreading the problem statement (or not reading it at all)
• stupidity

Submissions

VERY COOL PROBLEM: NOI '16 P6 - Computation

cool submissions:
VM7WC '16 #3 Silver - Can Shahir even get there?!
CCC '09 S4 - Shop and Ship
TLE 2018-19 P1 - Hello, World! (first 20p lmao)
Phantom's Python Challenge (ggggggggggggggggggggggggggggg and first 40p hehe)
UTS Open '15 #6 - Tetrahedra (bro why is this even 40p)
CCC '23 J5 - CCC Word Hunt (lmao myfirstpwogwam always works)
A Long Problem (1000th problem solved gg)
NOI '05 P6 - Lemon Tree Under the Moon (BRO I HATE THIS PROBLEM)
TLE 2018-19 P5 - Pure Functional Programming (hurray!!! gg cool problem) WHO REJUDGED MY SUBMISSION >:(

these
this one is actually skill

Hello, World! (what)