Island Count

Given a 2D array binaryMatrix of 0s and 1s, implement a function getNumberOfIslands that returns the number of islands of 1s in binaryMatrix.

An island is defined as a group of adjacent values that are all 1s. A cell in binaryMatrix is considered adjacent to another cell if they are next to each either on the same row or column. Note that two values of 1 are not part of the same island if they’re sharing only a mutual “corner” (i.e. they are diagonally neighbors).

Explain and code the most efficient solution possible and analyze its time and space complexities.

Example:

input:  binaryMatrix = [ [0,    1,    0,    1,    0],
                         [0,    0,    1,    1,    1],
                         [1,    0,    0,    1,    0],
                         [0,    1,    1,    0,    0],
                         [1,    0,    1,    0,    1] ]
output: 6 # since this is the number of islands in binaryMatrix.
          # See all 6 islands color-coded below.

Constraints:

• [time limit] 5000ms
• [input] array.array.int binaryMatrix
• 1 ≤ binaryMatrix.length ≤ 100
• 1 ≤ binaryMatrix[i].length ≤ 100
• [output] integer

O(N) for both Time and Space Complexities.

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