ZCO2020 cutoff and score

general
42

I got 110 in pretests. I think cutoff will be 30 marks but not too sure.
Weird ordering was fairly straightforward and runs in O§.
Didnt get interleaving but Ik its a 3d dp soln

43

easier than last year ig

44

wait did you give it from mumbai?

45

Hey everyone, who is the overexcited who cleared the spreadsheet. Whoever did, just understand, it was for good sake. Control your

46

A couple of my friends and I should be getting around 100-110.

The first question was something you could crack by looking at the patterns of numbers generated for each p.

The second question was something that involved solid DP, but I didn’t have any time left to implement the solution. Guess I’ll have to be happy with a 100😂

What do you think the cutoff will be this year?

47

Dude see his profile he is from Bihar. Although the guy who sat beside me looked like him. I gave it from Mumbai

48

Uh were you in room 215?

49

I was in B117 or B17 i dont remember

50

I noticed how people kept messing with the provisional scores sheet, so I decided to make a google form instead.

Just add your scores here.

You can view all the reponses here.

Here you can view the summary of the responses as well. (You get the option to see this after submitting a response too)

4 Likes
51

genius idea(a form)

people even tried to mess the zio sheet.I wonder how the previous year sheets are so clean

1 Like
52

This looks like the same case as that of ZIO. Most ppl getting 100+. I am afraid the cutoff will be higher this time aswell.

53

Okay, the problems were far different than previous years. I could solve some of the previous ones, but not today. I think I got the first one partially right, but I have no confidence. But I am going to learn and practice from now on. IOI is not the end!:blush:
(PS : I learned C++ basics and basic algorithms just this week, so I was not really prepared. Great 1experience though!)

1 Like
54

Actually, this type of ordering is one that is used in the iterative implementation of FFT, it’s called a bit-reversal permutation. Simply represent idx as a p-bit binary number, reverse this number that is the answer to the question. [1]

I never expected learning FFT to be helpful in ICO. XD
Also, I’m pretty sure that is how the setters came up with the question. :P

[1] Page 918 - Introduction to Algorithms by Cormen, Leiserson, Rivest, Stein (CLRS)

5 Likes
55

Exactly which pattern did you work off of as I too saw a pattern but was unable to implement it efiiciently enough

56

I did this:
ull ans = 0;
for(int i = 0; i < str.size(); i++){
int val = str[i] - ‘0’;
if(val)
ans += (1 << i);
}
I got only 20% why?
Addition can’t handle it?

57

I got 70 (60+10). I solved most of the questions but there were many runtime errors :-(. Will I clear the cutoff?

58

Oh man, I feel terrible for this.
The problem lies in the 1<<i part. This is of long long datatype but rather int since 1 by default is an int and any bitshifts that are done are on an int and when i > 32 (which is possible according to constraints), it will overflow.

Using 1LL << i instead will fix it.

2 Likes
59

let’s pray cutoff is 30 atleast

1 Like
60

Ahh I was really confused by this during the test. Initially, I was doing ((long long)(1<<i)) and I got wa but i didn’t understand why. Later, I fixed it to (long long)1<<i and it passed though I didn’t know what error was

61

In the first problem you just have to rotate the bits in the binary representation of the idx by p, which is the power of 2.You can do that pretty easily using bit manipulations to make it efficient!