This problem is an implementation of the famous flood-fill algorithm. So we're given a matrix, and we need to traverse an element's neighbors, and then repeat. It's always beneficial to think through a smaller input first.
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const input = [
[1, 1, 1],
[1, 1, 1],
[1, 0, 0]
OUTPUT
:001 > Cmd/Ctrl-Enter to run, Cmd/Ctrl-/ to comment