# Virus Detected - Please execute anti-virus code

Virus Detected!!!

Your computer, which is represented by the grid pictured, has been infected. The bugs are clearly marked. It's your job to inject your awesome anti-virus code in the proper computer address (grid coordinate).

This virus is smart though. You must follow these instructions to succeed:

Rules of Play

1. Every bug on the grid is associated with an anti-virus symbol, which is always horizontally or vertically adjacent to it.

2. No anti-virus symbol can be horizontally, vertically or diagonally adjacent to another anti-virus symbol.

3. The numbers for each column/row indicate the total number of allowable anti-virus symbols within that column/row (a checksum sort of).

4. The final solution will have 20 anti-virus symbols.

5. An anti-virus symbol can only be associated with one bug, but a bug can be adjacent to more than one anti-virus symbol.

Hint: A completed sample puzzle for you to study.

Good Luck. There is one, and only one solution to fixing your computer.

I suppose your answers could be represented by a simple 0, 1 grid.

• Going to add a new rule to the next version, which should make it quite challenging. You guys are good! I really thought this would stay unsolved for a LITTLE while, sheesh. lol ok stay tuned...working version 2. – John S. May 1 '19 at 16:17

Incidentally, this is Tents, game ID 10x10:acabc_acle_ffeckhad_e,2,2,3,0,4,1,3,1,3,1,5,0,3,1,2,2,1,3,1,2

The logic in detail:

Every AV must be adjacent to a bug, so only the spaces marked ? are legal spots for AVs:

    ABCDEFGHIJ
r10 ?*?·?*?*?· 5
r9  *?·?**?*?· 0
r8  ?*?·??·?·· 3
r7  ??·?*?··?· 1
r6  **?·??·?*? 2
r5  ??··?*?·?· 2
r4  ?*?·?*??·· 1
r3  ·?···??*?· 3
r2  ···???*?*? 1
r1  ··?**??·?· 2
2230413131

Row 10 has 5 spaces for AVs and its checksum is 5, so all spaces must be AVs. I10 and C10 are each adjacent to exactly one bug and must be associated with them. A10 and G10 could have been associated with one of two bugs, but one of those was just claimed, so they must belong to A9 and F10 respectively. E10 belongs to E9 the same way. All spaces adjacent to AVs must not be AVs.

    ABCDEFGHIJ
r10 V*<·V*<*<· 5
r9  *···**·*·· 0
r8  ?*?·??·?·· 3
r7  ??·?*?··?· 1
r6  **?·??·?*? 2
r5  ??··?*?·?· 2
r4  ?*?·?*??·· 1
r3  ·?···??*?· 3
r2  ···???*?*? 1
r1  ··?**??·?· 2
2230413131

F9 and H9 each have only one adjacent available space, so those spaces must be their AVs. All spaces adjacent to AVs must not be AVs. Column D's checksum is 0, so D2 and D7 must not be AVs.

    ABCDEFGHIJ
r10 V*<·V*<*<· 5
r9  *···**·*·· 0
r8  ?*?··^·^·· 3
r7  ??··*····· 1
r6  **?·??·?*? 2
r5  ??··?*?·?· 2
r4  ?*?·?*??·· 1
r3  ·?···??*?· 3
r2  ····??*?*? 1
r1  ··?**??·?· 2
2230413131

E7 has only one adjacent available space, so E6 must be its AV. Spaces adjacent to E6 can't be AVs, which leaves the bug at F5 with only G5 available for its AV. G5 then eliminates G4, H4, and H6.

    ABCDEFGHIJ
r10 V*<·V*<*<· 5
r9  *···**·*·· 0
r8  ?*?··^·^·· 3
r7  ??··*····· 1
r6  **?·^···*? 2
r5  ??···*<·?· 2
r4  ?*?·?*···· 1
r3  ·?···??*?· 3
r2  ····??*?*? 1
r1  ··?**??·?· 2
2230413131

Column E has two AVs, two spaces, and a checksum of 4, so the remaining spaces must be AVs, each belonging to its only adjacent bug. Eliminate spaces adjacent to AVs, and row 3 can be deduced from its checksum.

    ABCDEFGHIJ
r10 V*<·V*<*<· 5
r9  *···**·*·· 0
r8  ?*?··^·^·· 3
r7  ??··*····· 1
r6  **?·^···*? 2
r5  ??···*<·?· 2
r4  ·*··>*···· 1
r3  ·^····X*X· 3
r2  ····V·*·*· 1
r1  ··?**·?·?· 2
2230413131

and the rest of the grid falls into place:

• Column J

• Column I

• Row 6

• Column C

• Row 1

• Row 8

• Row 7

• Column A

• Column B

The final layout:

    ABCDEFGHIJ
r10 V*<·V*<*<· 5
r9  *···**·*·· 0
r8  ·*<··^·^·· 3
r7  V···*····· 1
r6  **··^···*< 2
r5  ·^···*<··· 2
r4  ·*··>*···· 1
r3  ·^····V*<· 3
r2  ····V·*·*· 1
r1  ··>**···^· 2
2230413131

• If this had been my puzzle, I would give this the Accept, because it explains how the solution was arrived at. – Jeff Zeitlin May 1 '19 at 12:03
• Awesome! I have some great links to these puzzles if you want to study to make your own. The highest I was ever able to do was 30 x 30 , and it was a lot of trial and error. – John S. May 1 '19 at 12:25
• @AuxTaco , you solved that very methodically. I liked the way you explained the steps for others to study. Thanks for providing the solution! – John S. May 1 '19 at 12:27
• Might be font dependent, but on my browser, the ✲ character is not fixed-width, which makes your diagrams very hard to read. I suggest just using a standard * instead... – Darrel Hoffman May 1 '19 at 15:54
• @DarrelHoffman Done. – AuxTaco May 1 '19 at 18:23