<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:
        visit={}
        cnt=0
        q=deque([])
        for i in range(len(grid)):
            for j in range(len(grid[0])):
                if grid[i][j]=='0':
                    continue
                if (i,j) in visit:
                    continue
                q.appendleft((i,j))
                visit[(i,j)]=cnt
                while q:
                    u,v=q.pop()
                    
                    if u-1>=0 and grid[u-1][v]=='1' and (u-1,v) not in visit:
                        q.appendleft((u-1,v))
                        visit[(u-1,v)]=cnt
                    if u+1<len(grid) and grid[u+1][v]=='1' and (u+1,v) not in visit:
                        q.appendleft((u+1,v))
                        visit[(u+1,v)]=cnt
                    if v-1>=0 and grid[u][v-1]=='1' and (u,v-1) not in visit:
                        q.appendleft((u,v-1))
                        visit[(u,v-1)]=cnt
                    if v+1<len(grid[0]) and grid[u][v+1]=='1' and (u,v+1) not in visit:
                        q.appendleft((u,v+1))
                        visit[(u,v+1)]=cnt
                    #print(len(q))
                cnt+=1
        return cnt
            
        
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