DRCHEF - Editorial

editorial
, , , ,
43

thank you so much @anon52057084

44

hey even i got 6,7,9 wrong test cases, but for your test case i get answer as 4 can u check my solution here

45

Thank you for helping me out.

1 Like
46

This worked for me as well. But what were the test cases that we missed? OR Why did we add this 2*, i didn’t get it yet. Can you please tell the logic behind this **2 ** * p[i] >= x ?

48

Can someone tell me the answer of this test case?
1
2 4
7 14
The problem is accepting 3 as the answer whereas the answer should be 4.

  • If you give 4 cures in day 1, next day you can give only 6 cures because population becomes (7-4)*2=6. so in day 2 you can give 6 cures. On day 3, you can give 12 cures which is less than 14 so total 4 days is required. In no ways you can give all 7 cures in second day.
49

Try:
1
2 10
9 18
Ans: 2

50

On the day 2 you can send delivery man to 2nd country and can give 8 cures.

51

It means for second country you require 2 days because population is 14 so the answer is still 4

52

[CodeChef: Practical coding for everyone]
Can someone find error in my code. 2 test cases failing.Can somebody give me a failed test case…

53

A very simple solution:
https://www.codechef.com/viewsolution/35417013
see line number 22 to 47

Only 2 if conditions inside the for loop used to iterate sorted array.

54

WHY ll= x/2+x%2 ; why not ll=x ??

55

sorry i was wrong …my bad :sweat_smile:
on first day we send our delivery man to second country now we have 8 vaccine, ( 7 infected in country 1st and 14 infected in country 2nd) ,then on second day we send him to 1st country now we have 14 vaccine ( 0 infected in 1st country and 14 in 2nd country) , on third day we send him to cure 2nd country. I hope it’s clear now.

56

In subtask 2, it think it should be 2 * Ai >= x .

57

I presume you are asking if we can deliver to that country if 2*a_i=x. Yes, we can. We can deliver to that country while doubling x or at the end. Either way it accounts for only 1 day for that country. My algorithm choses to deliver at the end.

1 Like
58

I get you. Even I was thinking the same, I know many have done just hit and trail. I tried to get a proof and I submitted it assuming maximum population will always have enough people to be cured so that we can every time double supply for some country having less population.

@sudipandatta can you provide me some valid argument to prove ? :slight_smile: it’d be helpful

59

Thanks @rudraksh26

60

Help!
Please correct if I am wrong.
As per question only way of doubling the x is to deliver the cure to a country that has infected_population > =x and that countries infected_population decrease by x and become double (or initial population). But when we will cure the last country it is possible our x can drop down at last day.
Example test case:
n=3 x=30
14 55 111

day 1> x=30 ar=[14, 55, 111] deliver x to 110 and it will become 110 next day again
day 2> x=60 ar=[14, X, 111] deliver x to 55
day 3> x=110 ar=[14, X, 1] deliver x to 111
day 4> x=220 ar=[14 ,X,2] deliver x to 2
day 5> x=4 ar=[14, X, X] deliver to 14
day 6> x=8 ar=[6, X, X]
day 7> x=16 ar[X,X,X]

But the correct ans is 5 days
can anyone help me under the algorithm because I think I am missing something.
I think as if the author has just taken x=ar[n-1]*2 at last without taking the reducing population of ar[n-1] in consideration.

61

Read the last line @ezio112

62

Try this TC:
1
3 7
3 14 28
ans is 4 days
your solution will give 5 days
reason: you are checking for (x/2) which gives 3 and you are starting from 1st country instead of 2nd country you should do (x+1)/2 in case of odd x and x/2 in case of even x.

63

thanks a lot man!!