Counting Islands

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MATRIX

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### Problem

Given a 2D grid `grid`

of 1s (land) and 0s (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically.

You may assume all four edges of the grid are surrounded by water.

### Examples

`numIslands([ [1, 1, 0], [1, 0, 0], [0, 1, 1] ]) // returns 2 /* There are two islands in the grid. The first island is at [(0,0), (0,1), (1,0)]. The second island is at [(2,1), (2,2)]. */`

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