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57 lines
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57 lines
2.0 KiB
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<p>给你二叉树的根节点 <code>root</code> 和一个整数 <code>distance</code> 。</p>
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<p>如果二叉树中两个 <strong>叶</strong> 节点之间的 <strong>最短路径长度</strong> 小于或者等于 <code>distance</code> ，那它们就可以构成一组 <strong>好叶子节点对</strong> 。</p>
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<p>返回树中 <strong>好叶子节点对的数量</strong> 。</p>
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<p> </p>
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<p><strong>示例 1：</strong></p>
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<p> </p>
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<p><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/07/26/e1.jpg" style="height: 321px; width: 321px;"></p>
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<pre><strong>输入：</strong>root = [1,2,3,null,4], distance = 3
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<strong>输出：</strong>1
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<strong>解释：</strong>树的叶节点是 3 和 4 ，它们之间的最短路径的长度是 3 。这是唯一的好叶子节点对。
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</pre>
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<p><strong>示例 2：</strong></p>
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<p><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/07/26/e2.jpg" style="height: 321px; width: 441px;"></p>
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<pre><strong>输入：</strong>root = [1,2,3,4,5,6,7], distance = 3
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<strong>输出：</strong>2
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<strong>解释：</strong>好叶子节点对为 [4,5] 和 [6,7] ，最短路径长度都是 2 。但是叶子节点对 [4,6] 不满足要求，因为它们之间的最短路径长度为 4 。
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</pre>
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<p><strong>示例 3：</strong></p>
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<pre><strong>输入：</strong>root = [7,1,4,6,null,5,3,null,null,null,null,null,2], distance = 3
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<strong>输出：</strong>1
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<strong>解释：</strong>唯一的好叶子节点对是 [2,5] 。
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</pre>
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<p><strong>示例 4：</strong></p>
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<pre><strong>输入：</strong>root = [100], distance = 1
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<strong>输出：</strong>0
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</pre>
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<p><strong>示例 5：</strong></p>
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<pre><strong>输入：</strong>root = [1,1,1], distance = 2
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<strong>输出：</strong>1
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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>tree</code> 的节点数在 <code>[1, 2^10]</code> 范围内。</li>
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<li>每个节点的值都在 <code>[1, 100]</code> 之间。</li>
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<li><code>1 <= distance <= 10</code></li>
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</ul>
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