Some good test cases:
2 8
3
01100011
00011000

1 2
0
00

Edited by author 07.02.2021 19:15

8 10
4
0000011000
0000110000
0000011000
0000110000
0000000000
0000000000
0000000000
0000000000
You should also try switching N and M (10 8)

Edited by author 08.02.2021 16:48

10 10

5
0000000000
1000000000
1100000000
0111100000
0010110000
0000000000
0000000000
0000000000
0000000000
0000000000

AC finally!!! I used a randomized approach, but in the end, I needed to use a special seed. Nice problem, but unfortunately, I wasn't able to find test 74 to share here.