[Question] Mathematics × Programming Competition #8 [問題] 數學 × 程式編寫比賽 (第八回)

in contest •  last year

Good News!

Thanks to @steemstem , the sponsored prize has been doubled!

Please refer to the "Prizes" section for details.


感謝 @steemstem 慷慨支持,贊助金額由是次比賽起增加一倍!


Mathematics × Programming Competition #8

Designed by @nicolemoker

13/10/2017 UTC 15:00 - 20/10/2017 UTC 15:00

For Chinese version please scroll to the bottom. 中文版請見文末。


Ken has a four-digit calculator which displays numbers using the seven-segment-display. For example the number 159 is displayed as

Note that 159 is displayed as 0159

Suppose we want to use non-transparent cards to represent all the possible 4-digit numbers from 0000 to 9999. Each card will show one 4-digit number, where the numbers are written using seven-segment-display. However when some cards are rotated 180°, a new number can be formed. For example when the card 0159 is rotated 180°, it becomes 6510.

Note that it is acceptable for the ‘1’ to be displayed on the left hand side

Considering the possibility of rotating a card 180°, what is the minimum number of non-transparent cards required to represent all the possible 4-digit numbers from 0000 to 9999?

Answer submission

Please submit your answer through this link.


  • This competition will last for 7 days. After that, no more submission will be accepted.
  • Participants who submit the answer as a comment below this post will be disqualified.
  • Participants can submit an unlimited number of solutions, however only the latest answer will be considered.
  • You have to upvote this post in order to be eligible for the competition.


  • The three fastest contestants would win the first prize, second prize and third prize respectively.
  • Other contestants who gave the correct answer would enter a lucky draw. 5 winners will be drawn.
  • Those who resteemed this post will have 400% higher chance to win in the lucky draw.
  • @kenchung reserves all the rights to disqualify any suspected cheating players and to decide the distribution of prizes among the winner(s).
Name of prizeMax no. of prizesSBDSP (sponsored by @steemstem ! )
First prize1SBD payout of this post / n15
Second prize1SBD payout of this post / n10
Third prize1SBD payout of this post / n5
Consolation prize5SBD payout of this post / n0

where n is the total number of winners in this competition. n = min (number of participants getting the correct answer, 8).

The steemSTEM project (@steemstem) is a community-supported project aiming to increase the quality and the visibility of STEM (STEM is the acronym for Science, Technology, Engineering and Mathematics) articles on Steemit. Please support steemSTEM by following @steemstem and joining the chat channel. You can also consider joining a private curation trail to further support steemSTEM by asking about it in the chat channel. In order to further promote the use of the chat channel, I will stop announcing the time of next competition via a post. Instead I will announce the time in advance in the chat channel!

數學 × 程式編寫比賽 (第八回)

Designed by @nicolemoker

13/10/2017 UTC 15:00 - 20/10/2017 UTC 15:00










  • 此比賽為時7天,其後將不會再接受新答案。
  • 嚴禁在回覆公開答案,否則將被取消資格。
  • 參加者可以重覆提交答案,但比賽終結時只會考慮最後提交的答案。
  • 你必須upvote此帖方能參加比賽。


  • 最快給出正確答案的三名參賽者將分別獲得一等獎、二等獎和三等獎。
  • 其他給出正確答案的參賽者將可參與抽獎。5名參賽者將被選出。
  • Resteem此帖文者將有額外400%的得獎機會。
  • 本人保留一切最終權利,包括但不限於取消任何疑似作弊者的資格並決定獲獎者的獎勵分配。
獎項獎項數目SBDSP (由 @steemstem 贊助!)
一等獎1此帖文的 SBD 金額 / n15
二等獎1此帖文的 SBD 金額 / n10
三等獎1此帖文的 SBD 金額 / n5
安慰獎5此帖文的 SBD 金額 / n0

其中 n 是本比賽中得獎者的總數。n = min (答對人數, 8)。

steemSTEM(@steemstem)是一個由steemit社群支持的項目,旨在宣傳STEM(STEM是科學,技術,工程和數學的首字母縮略詞)。 請追蹤 @steemSTEM 以及加入聊天頻道來支持steemSTEM。你還可以透過加入自動點讚系統來在為了進一步支持steemSTEM,詳情請在聊天頻道內向負責人士查詢。為了推廣聊天頻道的使用,我將不再透過發文來宣布下一場比賽的時間,我會在聊天頻道中提前公佈比賽時間。

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print(int(sum(map(lambda d: 0.5 if d != ''.join(map(lambda i:'012xx59x86'[int(i)], d[::-1])) and ''.join(map(lambda i:'012xx59x86'[int(i)], d[::-1])) in ['%04d' % x for x in range(0, 10000)] else 1 , ['%04d' % x for x in range(0, 10000)]))))





submitted, voted and resteeeeeeeeeeeeeeem!


thanks for joining (again) ! ;)

Nice! I submitted my answer! 😼


great! :)

It seems it's not so late. I decide to reply first to get a nice position:)
Btw, I see there may be a mistake on competition period
"13/10/2017 UTC 15:00 - 20/11/2017 UTC 15:00"
I think it should be:
"13/10/2017 UTC 15:00 - 20/10/2017 UTC 15:00".


just to remind you that your final position depends on the time of your answer submission through the google form, not the timestamp of your comment here ;)


Thank you, already summited


thanks for spotting the mistake, I have just updated it :)


他说你的日期写错了,13/10/2017 UTC 15:00 - 20/11/2017 UTC 15:00,截止日期应该是 20/10/2017 UTC 15:00 吧?



I'm not able to answer this question but I'll resteem this because it's a good question


thanks so much!


sure you can. you can write them all down one at a time, and hope you can identify a pattern (or hope you don't make a counting error). Or, you can learn how to code. This is a simple one through coding.

Am I late? submitted and resteemed~~


not quite late i guess, but even if the first 3 spots have been taken, you can still have the chance to get a random prize!



thanks for joining!

I hate maths, I'm probably lost here. Let me come and be going 🏃🏃🏃🏃🚶🚶


sorry to hear that you hate maths, hopefully this question did not make you hate it more! haha

commenting so I can resteem later, if I remember and am able to.


great :) thanks for joining


It won't let me resteem. Timed out the other day. Oh well.

submitted one day later. Hope my answer is correct and luckily get the prize=]
btw I've use some excel function to do it. Hope my logic is correct haha.


ye I think it is possible to use Excel to solve this question :) hope that you can win!




May I use contents of this post in my blog for illustrating the solution?(in the future, not now). I will comment where I quote them from.


ye sure!

submitted my answer :)
luckily i saw your announcement 1 hour ago in the steemstem channel, so I can catch your post on time!


ye if you join the steemstem channel you would know the time of competition in advance!

waiting to see the answer :) hopefully got it right