In the June Lunch time challenge problem name Form Rational to binary problem code REALBIN.

I think there is some problem with editorial of this problem as according to problem statement, we have to say whether a number can become 0 or 1 on addition of several rational numbers, in short we have to check number is rational or not.

In this questions editorial if we give a = 1 and b = 5 it is giving No as answer which should not be the case as 1/5 is rational number 0.2 and subtracting 0.2 from it will give 0 so it is a correct input.

But all inputs consisting powers of 5 are neglected in this problem.

I am unable to find out why this is happening

Please help me clear this out.

if you give 1/5 then he can add it, so now it will become 2/5

so if 1/5 is added 4 times to 1/5 it becomes 1, that is for a finite value N (N = 4 here) X becomes equal to 1 hence answer should be âYesâ. Please explain

it depends on divyam to add or subtract

@puneet18

Bro you choose a value and someone else(divyam) will choose which operation to perform . He donât want you to win .

Like in case of 1/5 you choose X=1/5 , oviously he will not choose to substract as the value will become â0â and you/chef will win , so he will add 1/5 âŚ now our initial value become 2/5 , if you will choose X = 1/5 again he will substract it from 2/5 resulting our intial vale to be 1/5 and this will run infinitely.

he donât want you to win , so he will add at this point .

divyam donât want to make it 0 or 1

OhâŚgot it now thanks manâŚ

If we take the example, X = 0.2. As you said, if we take Y = 0.8 and add it to X, then, we will get the answer to be 1. But, the problem statement states that Y can either be added to X, or subtracted from X. That choice lies with Divyam. So, Divyam would subtract in this case, so that, Chef does not win.

The question does nât ask if itâs possible to reach 0 or 1 in finite steps.

Divyam can use the operations âaddâ or âsubtractâ in such a way that he can avoid 0 or 1.

For eg. - if x = 1/5 and Chef gives him 1/5, then he can add it to make x = 2/5

Suppose again x = 1/5 is given, then he can subtract 1/5 from x and then x becomes 1/5.

So, no matter how many times you give 1/5, Divyam can go from 1/5 to 2/5 and then return to 1/5 again.

This problem was one of the most beautiful problem ,

i took 8 submission for the correct one ,

my first approach was to think mathematically ,

basically upto 4th try i was trying mathematical relation finding ,

then i realised ONLY 0.5 is the number who can normally jump to 1 or 0 ,

then i observed 0.25 and 0.75 can be brought to 0.5 with the given condition ,

and further realised B just have to be power of 2

but if we choose 1/3 then also chef will win , so How come people are using odd even logic here???

chef will not win in this case buddy . You will not be able to make 1/3 to 1 or 0

ok I will once again go through the question

Currently , I am not able to understand

actually b should have only one factor which is 2 and donât say problem have error coz u didnât understood and yes donât cheat in contest i know you cheated in tic tac toe of june lunchtime