perplexus.info :: General : Lights Out! (2)

Lights Out! (2) (Posted on 2022-10-31)

Imagine there is a 7x7 grid of lights, and only the middle in the grid is on.

The lights are wired such that when you flip the switch for one light (from on to off or off to on) the others next to it (not diagonally) flip as well.

Using this weird wiring of lights, what is the fewest number of switch changes it takes to turn all the lights off, and which lights should you switch?

Note: Assume all the switches work in the manner explained, and there is one switch for each of the lights.

Submitted by K Sengupta

Rating: 5.0000 (1 votes)

Solution: (Hide)

The required fewest number of switch changes is 17.
For an explanation, refer to the solution submitted by Charlie in this location.
An extension to the problem was provided and solved by Steven Lord in this location with Brian Smith's correction here.
Charlie has provided a solution to the extended version of the problem here and here.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
No Subject	K Sengupta	2023-05-15 12:22:55
No Subject	K Sengupta	2023-05-15 12:22:53
re: No Subject	Usytdm	2023-05-15 04:28:52
re: comment	Bastui	2023-05-15 04:25:07
re: further extension...	Loasm	2023-05-15 04:20:20
re: continuing the fun	Kisydua	2023-05-15 04:12:46
continuing the fun - edited	Steven Lord	2022-11-18 19:33:47
continuing the fun	Steven Lord	2022-11-18 06:02:45
further extension...	Steven Lord	2022-11-16 02:58:12
re(2): Cleaned-up code for the extension and an observation	Charlie	2022-11-14 14:18:01
re: Cleaned-up code for the extension and an observation	Brian Smith	2022-11-14 12:06:27
Cleaned-up code for the extension and an observation	Charlie	2022-11-13 11:32:26
Faster Method -- here's 17 and 19	Charlie	2022-11-11 22:01:34
comment	Steven Lord	2022-11-11 15:29:47
re(4): extension of the problem -- 13 and 15	Charlie	2022-11-11 14:02:56
re(3): extension of the problem	Charlie	2022-11-11 12:41:43
re(2): extension of the problem	Steven Lord	2022-11-11 10:45:13
re: extension of the problem	Brian Smith	2022-11-11 10:37:12
extension of the problem	Steven Lord	2022-11-11 04:34:13
No Subject	K Sengupta	2022-11-05 04:51:36
No Subject	boxnovel	2022-11-05 03:40:55
computer solution	Charlie	2022-10-31 10:31:43

Please log in:

Login:
Password:
Remember me:

Sign up! \| Forgot password

Search:

Search body:

Forums (1)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (17)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:


perplexus dot info