Find the number of islands

Given a boolean 2D matrix, find the number of islands.

What is an island?
A group of connected 1s forms an island. For example, the below matrix contains 5 islands

                 {1, 1, 0, 0, 0},
                        {0, 1, 0, 0, 1},
                        {1, 0, 0, 1, 1},
                        {0, 0, 0, 0, 0},
                        {1, 0, 1, 0, 1}

http://www.geeksforgeeks.org/find-number-of-islands/

http://www.geeksforgeeks.org/find-the-number-of-islands-set-2-using-disjoint-set/

Question 2: Connected Cells in a Grid

https://www.hackerrank.com/challenges/connected-cell-in-a-grid

https://www.macs.hw.ac.uk/~pjbk/pathways/cpp2/node80.html