122 lines
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122 lines
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HTML
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</style><!-- hexo-inject:begin --><!-- hexo-inject:end --></head><body><header><a href="/" class="logo-link"><img src="/logo.png"></a><ul class="nav nav-list"><li class="nav-list-item"><a href="/" target="_self" class="nav-list-link">ALL</a></li><li class="nav-list-item"><a href="/categories/leetcode/" target="_self" class="nav-list-link">LEETCODE</a></li><li class="nav-list-item"><a href="https://bearmiebear.blogspot.com" target="_blank" class="nav-list-link">BEAR</a></li><li class="nav-list-item"><a href="/atom.xml" target="_self" class="nav-list-link">RSS</a></li></ul></header><section class="container"><div class="post"><article class="post-block"><h1 class="post-title">leetcode-number-of-islands</h1><div class="post-meta"><div class="post-time">2020年4月21日</div></div><div class="post-content"><h3 id="200-__u5C9B_u5C7F_u6570_u91CF"><a href="#200-__u5C9B_u5C7F_u6570_u91CF" class="headerlink" title="200. 岛屿数量"></a>200. 岛屿数量</h3><p><a href="https://leetcode-cn.com/problems/number-of-islands/" target="_blank" rel="noopener">题目</a></p>
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<p>这种矩阵题现在第一反应就是用<a href="(https://zh.wikipedia.org/zh-cn/%E5%B9%BF%E5%BA%A6%E4%BC%98%E5%85%88%E6%90%9C%E7%B4%A2)">广度优先搜索</a>做，类似之前算和0之间的距离那题。遍历矩阵，遇到 1 就将 1 改成 0，然后广度优先搜索找出 1 相邻的所有 1，这就是一个岛屿，以此类推。</p>
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<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> collections</span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span>:</span></span><br><span class="line"> <span class="function"><span class="keyword">def</span> <span class="title">numIslands</span><span class="params">(self, grid)</span> -> int:</span></span><br><span class="line"> rows = len(grid)</span><br><span class="line"> <span class="keyword">if</span> <span class="keyword">not</span> rows:</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span></span><br><span class="line"> cols = len(grid[<span class="number">0</span>])</span><br><span class="line"> islands = <span class="number">0</span></span><br><span class="line"> <span class="keyword">for</span> r <span class="keyword">in</span> range(rows):</span><br><span class="line"> <span class="keyword">for</span> l <span class="keyword">in</span> range(cols):</span><br><span class="line"> <span class="keyword">if</span> grid[r][l] == <span class="string">'1'</span>:</span><br><span class="line"> islands += <span class="number">1</span></span><br><span class="line"> grid[r][l] = <span class="string">'0'</span></span><br><span class="line"> neighbors = collections.deque([(r, l)])</span><br><span class="line"> <span class="keyword">while</span> neighbors:</span><br><span class="line"> x, y = neighbors.popleft()</span><br><span class="line"> <span class="keyword">for</span> x_, y_ <span class="keyword">in</span> [[x<span class="number">-1</span>, y], [x+<span class="number">1</span>, y], [x, y<span class="number">-1</span>], [x, y+<span class="number">1</span>]]:</span><br><span class="line"> <span class="keyword">if</span> <span class="number">0</span><=x_<rows <span class="keyword">and</span> <span class="number">0</span><=y_<cols <span class="keyword">and</span> grid[x_][y_] == <span class="string">'1'</span>:</span><br><span class="line"> neighbors.append([x_, y_])</span><br><span class="line"> grid[x_][y_] = <span class="string">'0'</span></span><br><span class="line"> <span class="keyword">return</span> islands</span><br></pre></td></tr></table></figure>
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