xxxx
___x
_xxx
_xxx

var visited = {}
var map = [
	[0, 1, 0, 1, 1, 1, 0],
	[1, 0, 0, 1, 1, 0, 1],
	[1, 1, 0, 0, 1, 1, 0]
]
var count = 0

function traverse(x, y) {
	visited[x + ',' + y] = true
	/** Checking right nodes */
	if ((x + 1 < map.length) && map[x + 1][y] === 1 && !visited[(x + 1) + ',' + y]) {
		traverse(x + 1, y)
	}
	/** Checking left nodes */
	if ((x - 1 >= 0) && map[x -1][y] === 1 && !visited[(x - 1) + ',' + y]) {
		traverse(x - 1, y)
	}
	/** Checking top nodes */
	if ((y + 1 < map[x].length) && map[x][y + 1] === 1 && !visited[x + ',' + (y + 1)]) {
		traverse(x, y + 1)
	}
	/** Checking bottom nodes */
	if ((y - 1 >= 0) && map[x][y - 1] === 1 && !visited[x + ',' + (y - 1)]) {
		traverse(x, y - 1)
	}
}

for (var i=0; i<map.length; i++) {
	for (var j=0; j<map[i].length; j++) {
		/** This node has been visited by traverse already or is not part of an island. Can be skipped */
		if (visited[i + ',' + j] || map[i][j] === 0) {
			continue;
		}
		/** This would indicate a new island that hasn't been traversed */
		if (!visited[i + ',' + j] && map[i][j] === 1) {
			count ++
			traverse(i, j)
		}
	}
}

 ........
 ..x..x..
 ..x..x..
 ..xxxx..
 ........

function countIslands(islandGrid) {
    let islandCount = 0;

    let visitedGrid = [];

    islandGrid.forEach(row => {
        zeroRow = row.map(elm => 0);
        visitedGrid.push(zeroRow);
    });

    for (let row = 0; row < islandGrid.length; row++) {
        for (let col = 0; col < islandGrid[row].length; col++) {
            //if square is land and not visited
            if  (islandGrid[row][col] === 1 && visitedGrid[row][col] === 0) {
                islandCount += 1;
                let queue = [[row, col]];
                
                while (queue.length > 0) {
                    let current = queue.shift();
                    let currentRow = current[0];
                    let currentCol = current[1];


                    //mark square as visited
                    visitedGrid[currentRow][currentCol] = 1;

                    //check if square is on grid, is land, is not visited

                    //e
                    if (currentCol + 1 < islandGrid[currentRow].length 
                            && islandGrid[currentRow][currentCol + 1] === 1 
                            && visitedGrid[currentRow][currentCol + 1] === 0) {
                        queue.push([currentRow, currentCol + 1]);
                    }

                    //s
                    if (currentRow + 1 < islandGrid.length
                            && islandGrid[currentRow + 1][currentCol] === 1
                            && visitedGrid[currentRow + 1][currentCol] === 0) {
                        queue.push([currentRow + 1, currentCol]);
                    }

                    //w
                    if (currentCol - 1 >= 0 
                        && islandGrid[currentRow][currentCol - 1] === 1 
                        && visitedGrid[currentRow][currentCol -1] === 0) {
                    queue.push([currentRow, currentCol -1]);
                    }

                    //n
                    if (currentRow - 1 >= 0 
                        && islandGrid[currentRow -1][currentCol] === 1
                        && visitedGrid[currentRow - 1][currentCol] === 0) {
                        queue.push([currentRow - 1, currentCol]);
                    }


                }
            }
        }
    }
    
    return islandCount;
}

X.X
X.X
XXX

1.2
1.2
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