NumberOfIslands.swift

		let islands = [[1,0,0,0,0],[0,0,1,1,0],[0,1,1,0,0],[0,0,0,0,0],[1,1,0,0,1],[1,1,0,0,1]]
		print(numberOfIslands(islands))

	func numberOfIslands(_ islands:[[Int]]) -> Int {
		if islands.count == 0 {
			return -1
		}

		var grid = islands
		var numberOfIslands = 0
		let maxRow = grid.count
		let maxCol = grid[0].count

		for row in 0..<maxRow {
			for col in 0..<maxCol {
				if grid[row][col] == 1 {
					numberOfIslands += 1
					grid[row][col] = 0
					var neighbours = [(Int,Int)]()
					neighbours.append((row,col))
					while !neighbours.isEmpty {
						let pos = neighbours.removeFirst()
						let newRow = pos.0
						let newCol = pos.1
						if newRow - 1 >= 0 && grid[newRow - 1][newCol] == 1 {
							neighbours.append((newRow - 1, newCol))
							grid[newRow - 1][newCol] = 0
						}
						if newRow + 1 < maxRow && grid[newRow + 1][newCol] == 1 {
							neighbours.append((newRow + 1, newCol))
							grid[newRow + 1][newCol] = 0
						}
						if newCol - 1 >= 0 && grid[newRow][newCol - 1] == 1 {
							neighbours.append((newRow, newCol - 1))
							grid[newRow][newCol - 1] = 0
						}
						if newCol + 1 < maxCol && grid[newRow][newCol + 1] == 1 {
							neighbours.append((newRow, newCol + 1))
							grid[newRow][newCol + 1] = 0
						}
					}

				}
			}
		}

		return numberOfIslands
	}