Chain Reaction (Part #2)

This is a sequel to Chain Reaction (Part #1), with the same setup, but a different flavor.

As in the previous part, you will be given a rectangular array representing a "map" with three types of spaces:

• "+" bombs: when activated, their explosion activates any bombs directly above, below, left, or right of the "+" bomb.
• "x" bombs: when activated, their explosion activates any bombs placed in any of the four diagonal directions next to the "x" bomb.
• Empty spaces "0".

The goal is simple: given a map, return the minimum number of bombs that need to be set off for all bombs to be destroyed by the chain reaction.

Let's look at some examples:

[
  ["+", "+", "+", "0", "+", "+", "+"],
  ["+", "+", "+", "0", "0", "+", "+"]
]

For the map above, the answer is 2; to explode all bombs you just need to set off one "+" bomb in the right cluster and one in the left cluster.

[
  ["x", "0", "x"],
  ["x", "x", "x"]
]

For the map above, the answer is 3; clearly setting off the three bottom "x" bombs is enough, and no less than three bombs suffice.

[
  ["x", "x", "x", "0", "x"],
  ["x", "x", "x", "x", "x"],
  ["x", "x", "x", "0", "x"]
]

For the map above, the answer is 3; setting off the three rightmost bombs in the middle row will do the trick.

Examples

min_bombs_needed([
  ["+", "+", "+", "0", "+", "+", "+"],
  ["+", "+", "+", "0", "0", "+", "+"]
]) ➞ 2

min_bombs_needed([
  ["x", "0", "x"],
  ["x", "x", "x"]
]) ➞ 3

min_bombs_needed([
  ["x", "x", "x", "0", "x"],
  ["x", "x", "x", "x", "x"],
  ["x", "x", "x", "0", "x"]
]) ➞ 3

Notes

• Note that both "+" and "x" bombs have an "explosion range" of 1.
• To limit the difficulty, in this challenge each map will have only "+" or only "x" bombs. The more challenging case of maps with both "+" and "x" bombs will be part 3!
• Figuring out what to do is half the fun, but if you'd prefer to just handle the coding, a hint on to how to attack this challenge can be found in the comments.