Physics noob tries to get better (ft.John rennie)

satan 29

5:29 AM

@JohnRennie hi sir

John Rennie

@satan29 hi :-)

satan 29

sir have you worked with Pygames?

John Rennie

No, sorry :-(

satan 29

ok, no problem

@JohnRennie @JohnRennie sir can you help me in downloading the module

John Rennie

pygames? Can't you just use pip ?

satan 29

5:38 AM

it s sayinng pip is not recognizable...

i tried python -m pip install too

then it said python not found

John Rennie

Your path is wrong or python.exe isn't on the path.

satan 29

how to check path? and change it?

John Rennie

Are you working ina command prompt?

satan 29

yes'

John Rennie

I would close the current command prompt and open a new one. Then type python and press enter and see what happens.

If you get a command not recognised error then the problem is the path.

satan 29

5:43 AM

i get a blank output

John Rennie

Can you remember where you installed Python? What directory?

@satan29 a blank output?

Ah, OK, yes Win10 does that.

It means the problem is the path. How do you normally run Python? From the Start menu? From a desktop icon?

satan 29

desktop icon

should i check the location?

John Rennie

Yes, right click the icon and choose Properties and see what it is running.

satan 29

"C:\Users\Shreshth Mehrotra\AppData\Local\Programs\Python\Python39\"

John Rennie

OK, in your command prompt type:

path="C:\Users\Shreshth Mehrotra\AppData\Local\Programs\Python\Python39\";%path%

satan 29

5:48 AM

blank output

John Rennie

Now type python

satan 29

it gave me some info about python

John Rennie

Ok, it's working.

type exit() to exit from Python.

python -m pip install should work now.

Shall I explain what the path command did?

satan 29

sir before that

wait

John Rennie

Yes ... ?

satan 29

5:53 AM

John Rennie

Isn't it just pygame not pygames

satan 29

OOF yes

installed now

John Rennie

:-)

satan 29

6:28 AM

@JohnRennie hi sir'

one problem

codeforces.com/problemset/problem/1497/A

i have got the logic.

but theres one slight issue

t=int(input())
for i in range(0,t):
    n=int(input())
    i=[]
    d=[]
    for j in range(0,n):
        y=int(input())

        if(y in i):
            d.append(y)
        else:
            i.append(y)
    i.sort()
    d.sort()
    l=i+d
    for k in range(0,n):
        print(l[k],end=" ")

sir try this for one test case

t=1, n=7

but the input here

is like this

1

7

4

2

0

1

3

7

i want the input to be like this:

1

7

4 2 0 1 3 3 7

so i tried this code:

t=int(input())
for i in range(0,t):
    n=int(input())
    i=[]
    d=[]
    for j in range(0,n):
        a=input()
        m=a.split()
        for y in range(0,len(m)):
            print(m[y])
            if(m[y] in i):
                d.append(m[y])
            else:
                i.append(m[y])
    i.sort()
    d.sort()
    l=i+d
    for k in range(0,n):
        print(l[k],end=" ")

John Rennie

Your loops look odd ...

The outermost loop is range(0,t) to loop over all t tests - so far so good.

Then for each test you read the data using:

n = int(input)
alist = input()
a = split(a)

So now n is the number of integers in the list and a is the list.

satan 29

a=split(a)?

    a=input()
    m=a.split()

sir my this part

is correct

John Rennie

Oops, a = split(alist)

satan 29

i tied debugging

@JohnRennie rught

John Rennie

@satan29 yes, but you are doing that inside a loop:

for j in range(0,n):

satan 29

6:37 AM

hmm

John Rennie

So you're calling split() n times in each test.

satan 29

i gotcha

fixxed niw

@JohnRennie sir ill be back in a while

but pls meanwhile check my submission and have a look at the error message

John Rennie

I need to drop out to work for a bit ...

satan 29

codeforces.com/profile/UltraNoobCoder2969

satan 29

8:04 AM

@JohnRennie hi

John Rennie

@satan29 hi :-)

satan 29

sir can you look at the error now

John Rennie

satan 29

yes sir...wth does that mean

John Rennie

I guess it means that although you did find a valid solution it wasn't the optimal solution. i.e. there are multiple possible solutions.

satan 29

8:10 AM

oh

sir but my logic seems to be work...

otherwise it wouldve failed test case 2

@JohnRennie

John Rennie

Your logic certainly finds a solution otherwise it wouldn't pass tests 1 and 2. But does your logic find the best solution?

satan 29

8:27 AM

what do you mean by "best"

John Rennie

The question says:

> For each test case print an array b1,b2,…,bn — the optimal reordering of a1,a2,…,an, so the sum of MEX on its prefixes is maximized.

But it doesn't define what it means by optimal ...

The error report says:

> wrong answer jury has better answer: jans = 4699, pans = 1753 (test case 24)

But it isn't clear what this means i.e. what are jans and pans ?

satan 29

@JohnRennie sir basically the reordering such that the mex sum is max

sir the thing we need to maximize is the mex sum

John Rennie

I don't think I can comment further as it isn't clear what the error report means.

You can copy and paste the test data from the report so you can try it on your PC.

satan 29

hmm

John Rennie

Am I missing something? Isn't it just a matter of sorting the array in ascending order?

satan 29

8:41 AM

if the values are duplicated, then this wont work

consider the test example

the duplicated values should be in the end

this is essentially what i have done @JohnRennie

kept the duplicated values in the end

John Rennie

9:01 AM

Hmm, OK, so start with the unique values in ascending order. Then append any duplicates also in ascending order.

satan 29

yes

actually, the ordering of the dupliates wont matter i guess

John Rennie

9:15 AM

This is my attempt. It's in the queue - the site seems slow today ...

num_tests = int(input())
for i in range(0,num_tests):
    n = int(input())
    in_list = list(map(int, input().split()))
    in_list.sort()

    # Copy the unique items into the output array, and copy any duplicates
    # into a separate array. We'll append the suplicates at the end.
    out_list = []
    dup_list = []
    last_num = -1
    for j in range(0,n):
        if in_list[j] != last_num:
            out_list.append(in_list[j])
            last_num = in_list[j]
        else:
            dup_list.append(in_list[j])

satan 29

whats the logic?

John Rennie

It should be clear from the comments ...

satan 29

oh oops

didnt see the comments

isnt that exactl what I have done?

John Rennie

I haven't looked at your code. I wanted to start with a clean slate.

If so my submission should fail with the same error you got.

satan 29

fair

John Rennie

9:22 AM

What concerns me is if dup_list also contains duplicates. Do we need to apply the same logic to dup_list i.e. move any duplicates in dup_list to the end?

satan 29

sir I dont suppose that will matter

John Rennie

The tests you're given contain no triplicated numbers so the issue didn't arise, but the test your code failed on does contain triplicates.

satan 29

the MEX value will remain constant after the last distinct element

John Rennie

Hmm.

Remember what I said about programming being partly experimental?

satan 29

XD yes

John Rennie

9:24 AM

If my submission fails with the same error as yours then I would try the experiment.

If it still fails all I've done is waste a bit of time.

satan 29

for reference, heres my current code:

t=int(input())
for i in range(0,t):
    n=int(input())
    i=[]
    d=[]
    a=input()
    m=a.split()
    for y in range(0,len(m)):
        if(m[y] in i):
            d.append(m[y])
        else:
            i.append(m[y])
    i.sort()
    d.sort()
    l=i+d
    for k in range(0,n):
        print(l[k],end=" ")

John Rennie

It's still waiting in the queue. I wonder if the "hardware issues" the site warns about mean everything is running slowly.

satan 29

yes I was about to say the same thing

John Rennie

OK, there's nothing we can do until the submissions run.

satan 29

iytll be ok within 1.5 hrs i guess

ill solve a few chess puzzles in the meantime :-)

John Rennie

10:12 AM

@satan29 BOOM!

Details here

satan 29

10:23 AM

sir, why did my code not work?

my output is damn weird for test case 3

what went wrong??

@JohnRennie

John Rennie

Let me have another look at your code ...

I note that you don't print a new line after each test output, though I guess that doesn't matter since it passed the first two trials.

Aha!

You are not converting the inputs to ints, so they are being sorted as strings not ints.

satan 29

huh

OHHH

t=int(input())
for i in range(0,t):
    n=int(input())
    i=[]
    d=[]
    a=input()
    m=a.split()
    for y in range(0,len(m)):
        if(int(m[y]) in i):
            d.append(int(m[y]))
        else:
            i.append(int(m[y]))
    i.sort()
    l=i+d
    for k in range(0,n):
        print(l[k],end=" ")

John Rennie

The Pythony way to do this is using the map() function i.e. something like:

list(map(int, input().split()))

This inputs a string, splits it, applies the function int() to every element and converts the resulting integers as a list.

satan 29

thats very useful, thanks

now it accepted my solution

John Rennie

:-)

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Physics noob tries to get better (ft.…