<p>Given an <code>m x n</code> 2D binary grid <code>grid</code> which represents a map of <code>&#39;1&#39;</code>s (land) and <code>&#39;0&#39;</code>s (water), return <em>the number of islands</em>.</p>

<p>An <strong>island</strong> is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> grid = [
  [&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;0&quot;],
  [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;],
  [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;],
  [&quot;0&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;]
]
<strong>Output:</strong> 1
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> grid = [
  [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;],
  [&quot;1&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;0&quot;],
  [&quot;0&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;],
  [&quot;0&quot;,&quot;0&quot;,&quot;0&quot;,&quot;1&quot;,&quot;1&quot;]
]
<strong>Output:</strong> 3
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == grid.length</code></li>
	<li><code>n == grid[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 300</code></li>
	<li><code>grid[i][j]</code> is <code>&#39;0&#39;</code> or <code>&#39;1&#39;</code>.</li>
</ul>

class Solution:
    def numIslands(self, grid: List[List[str]]) -> int:
        count = 0
        row, col = len(grid), len(grid[0])

        #bfs
        for i in range(row):
            for j in range(col):
                if grid[i][j] == "1":
                    count += 1
                    grid[i][j] = str(0)
                    queue = collections.deque()
                    queue.append([i, j])

                    while queue:
                        cur = queue.popleft()
                        moves = [[-1, 0], [1, 0], [0, -1], [0, 1]]
                        for move in moves:
                            q, k = cur[0] + move[0], cur[1] + move[1]
                            if 0 <= q < row and 0 <= k < col and grid[q][k] == "1":
                                queue.append([q, k])
                                grid[q][k] = str(0)
        return count

        #dfs
        # def dfs(i, j):
        #     grid[i][j] = str(0)
        #     moves = [[0, 1], [0, -1], [1, 0], [-1, 0]]
        #     for move in moves:
        #         q, k = i + move[0], j + move[1]
        #         if q < 0 or q >= row or k < 0 or k >= col:
        #             continue
        #         if int(grid[q][k]) == 1:
        #             dfs(q, k)

        # for i in range(row):
        #     for j in range(col):
        #         if int(grid[i][j]) == 1:
        #             count += 1
        #             dfs(i, j)
        # return count
21341