Get referred by a friend at Google, and then get scheduled for an HR interview soon after. That was nice and easy.

This was followed by a technical interview over the phone.

Not a great answer. So, it was finally declined without explicit explanation.

I think this is pretty normal for such a big company like Google. Nothing else to say.

Given a 2D matrix containing 0s and 1s, determine how many distinct "countries" exist within the matrix.

A "country" is defined as a contiguous group of identical values (either all 0s or all 1s) connected horizontally or vertically.

For example:

[[ 1, 1, 1, 0 ], [ 1, 1, 0, 0 ], [ 0, 0, 0, 1 ]]

This matrix contains 3 countries. One country is formed by the connected 1s, another by the connected 0s, and a third by the single isolated 1.

Another example:

[[ 1, 1, 1, 1 ], [ 0, 0, 0, 0 ], [ 1, 0, 0, 1 ]]

This matrix contains 4 countries. There are two separate groups of 1s, one group of 0s, and another isolated 1.