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50 lines
3.0 KiB
HTML
50 lines
3.0 KiB
HTML
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<p>给你一个二维字符网格数组 <code>grid</code> ，大小为 <code>m x n</code> ，你需要检查 <code>grid</code> 中是否存在 <strong>相同值</strong> 形成的环。</p>
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<p>一个环是一条开始和结束于同一个格子的长度 <strong>大于等于 4</strong> 的路径。对于一个给定的格子，你可以移动到它上、下、左、右四个方向相邻的格子之一，可以移动的前提是这两个格子有 <strong>相同的值 </strong>。</p>
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<p>同时，你也不能回到上一次移动时所在的格子。比方说，环 <code>(1, 1) -> (1, 2) -> (1, 1)</code> 是不合法的，因为从 <code>(1, 2)</code> 移动到 <code>(1, 1)</code> 回到了上一次移动时的格子。</p>
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<p>如果 <code>grid</code> 中有相同值形成的环，请你返回 <code>true</code> ，否则返回 <code>false</code> 。</p>
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<p> </p>
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<p><strong>示例 1：</strong></p>
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<p><strong><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/08/22/5482e1.png" style="height: 152px; width: 231px;"></strong></p>
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<pre><strong>输入：</strong>grid = [["a","a","a","a"],["a","b","b","a"],["a","b","b","a"],["a","a","a","a"]]
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<strong>输出：</strong>true
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<strong>解释：</strong>如下图所示，有 2 个用不同颜色标出来的环：
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<img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/08/22/5482e11.png" style="height: 163px; width: 225px;">
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</pre>
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<p><strong>示例 2：</strong></p>
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<p><strong><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/08/22/5482e2.png" style="height: 154px; width: 236px;"></strong></p>
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<pre><strong>输入：</strong>grid = [["c","c","c","a"],["c","d","c","c"],["c","c","e","c"],["f","c","c","c"]]
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<strong>输出：</strong>true
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<strong>解释：</strong>如下图所示，只有高亮所示的一个合法环：
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<img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/08/22/5482e22.png" style="height: 157px; width: 229px;">
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</pre>
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<p><strong>示例 3：</strong></p>
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<p><strong><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/08/22/5482e3.png" style="height: 120px; width: 183px;"></strong></p>
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<pre><strong>输入：</strong>grid = [["a","b","b"],["b","z","b"],["b","b","a"]]
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<strong>输出：</strong>false
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</pre>
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<p> </p>
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<p><strong>提示：</strong></p>
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<ul>
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<li><code>m == grid.length</code></li>
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<li><code>n == grid[i].length</code></li>
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<li><code>1 <= m <= 500</code></li>
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<li><code>1 <= n <= 500</code></li>
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<li><code>grid</code> 只包含小写英文字母。</li>
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</ul>
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