🔒 help with kattis question | Python | Page 1

dense patrol Sep 25, 2024, 2:24 AM

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https://open.kattis.com/problems/upsanddownsofinvesting
my solution works for the first two testcases but fails on the first real one.

To summarize the problem
given a graph you are supposed to find the peaks and throughs, i do this by calculating the number of consecutive changes in one direction so if i have the graph 5 6 9 8 5 4 i will collapse it to 2, -3.

I then iterate through the collapsed list and check if every i and i+1 is greater than the n or m (the number of consecutive rises/falls) they want and if so then it is a through. i cant think of a scenario where my solution fails can someone help me

x, n, m = list(map(int, input().split()))
n-=1
m-=1
l=list(map(int, input().split()))
upordown=[1 if ((l[i+1]-l[i])>0) else -1 if ((l[i+1]-l[i])<0) else 0 for i in range(len(l)-1)]
if (x==1) or (x==2):
    print("0 0")
else:
    collapsed=[]
    length=0
    for i in range(len(upordown)-1):
        if upordown[i]!=upordown[i+1]:
            length+=upordown[i]
            collapsed.append(length)
            length=0
        else:
            length+=upordown[i]
    collapsed.append(length+1 if length>0 else length-1)
    ind=0
    h=0
    l=0
    for i in range(len(collapsed)-1):
        ind+=abs(collapsed[i])
        if ((collapsed[i]>=n) and (abs(collapsed[i+1])>=n)):
            h+=1
        elif ((abs(collapsed[i])>=m) and (collapsed[i+1]>=m)):
            l+=1
    print(h,l)

ornate vortexBOT Sep 25, 2024, 2:24 AM

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dense patrol https://open.kattis.com/problems/upsanddownsofinvesting my solution works for th...

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@dense patrol

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dense patrol Sep 25, 2024, 2:28 AM

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if anyone has any questions on my approach plz ask ive been stuck on this stupid problem for like 2 days

patent marlin Sep 25, 2024, 2:43 AM

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dense patrol https://open.kattis.com/problems/upsanddownsofinvesting my solution works for th...

According to the problem, its n = 2, and m = 3. Even the sample output shows the m is a positive number. Maybe that's why?

dense patrol Sep 25, 2024, 2:45 AM

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2 is the number of consecutive rises and falls to be considered the peak and 3 is the number of consecutive falls and rises to be considered the through

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oh if ur talking about the collapsed array i absolute it before comparing in my if statement

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    for i in range(len(collapsed)-1):
        ind+=abs(collapsed[i])
        if ((collapsed[i]>=n) and (abs(collapsed[i+1])>=n)):
            h+=1
        elif ((abs(collapsed[i])>=m) and (collapsed[i+1]>=m)):
            l+=1

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im guessing i did something wrong here though

patent marlin Sep 25, 2024, 2:49 AM

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dense patrol im guessing i did something wrong here though

Do you have tests scripts that uses the sample inputs and checks against sample outputs?

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Does the kattis site have a test runner?

dense patrol Sep 25, 2024, 2:50 AM

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yeah but apart from the sample test cases the rest are hidden

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i pass the sample test case but fail the first hidden one

patent marlin Sep 25, 2024, 2:50 AM

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passed? with print statements?

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Are you not supposed to use functions and returns?

dense patrol Sep 25, 2024, 2:51 AM

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yeah like i got the same output as them

patent marlin Sep 25, 2024, 2:51 AM

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dense patrol yeah like i got the same output as them

does it show what is the expected output?

dense patrol Sep 25, 2024, 2:51 AM

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nope sadly

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i hate this site haha i want to know what testcases i failed

sand radish Sep 25, 2024, 2:54 AM

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hm it doesn't even show what's being printed?

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maybe there's an edge case where ppl would input n m 0 ?

dense patrol Sep 25, 2024, 2:54 AM

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sand radish hm it doesn't even show what's being printed?

yeah kattis is cringe like that

dense patrol Sep 25, 2024, 2:55 AM

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sand radish maybe there's an edge case where ppl would input n m 0 ?

nope n and m guranteed between 2 and 100

sand radish Sep 25, 2024, 2:55 AM

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I see

dense patrol Sep 25, 2024, 2:56 AM

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oh i just found a testcase i fail lol

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its when s is 3

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argh i made a change but now it solves 4 testcases instead of 2 lol

patent marlin Sep 25, 2024, 3:05 AM

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✨ progress ✨

crystal scaffold Sep 25, 2024, 3:10 AM

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Can you try adding "collapsed = [c + 1 for c in collapsed]" after "collapsed.append(length+1 if length>0 else length-1)" ?

dense patrol Sep 25, 2024, 3:13 AM

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sure

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that line was definitely the problem at least for testcase 3

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i tried changing it to

collapsed.append(length+1 if ((length>0)and upordown[-1]>0) else length-1 if ((length<0)and upordown[-1]<0) else upordown[-1])

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but it only solved two more cases haha

crystal scaffold Sep 25, 2024, 3:15 AM

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Actually I made a mistake

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for i, c in enumerate(collapsed):
if c > 0:
collapsed[i] = c + 1
elif c < 0:
collapsed[i] = c - 1

Can you try this change?

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I think the problem is an off-by-one error in how you measure the lenght of subsequent increases and decreases

dense patrol Sep 25, 2024, 3:18 AM

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yeah i think so too the collapse part of the code is wrong

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argh the fix doesnt seem to work though, failing on sample testcases

ornate vortexBOT Sep 25, 2024, 4:19 AM

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#🔒 help with kattis question