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38 lines
1.7 KiB
HTML
<p>You are given the <code>root</code> of a binary tree and an integer <code>distance</code>. A pair of two different <strong>leaf</strong> nodes of a binary tree is said to be good if the length of <strong>the shortest path</strong> between them is less than or equal to <code>distance</code>.</p>
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<p>Return <em>the number of good leaf node pairs</em> in the tree.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/07/09/e1.jpg" style="width: 250px; height: 250px;" />
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<pre>
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<strong>Input:</strong> root = [1,2,3,null,4], distance = 3
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> The leaf nodes of the tree are 3 and 4 and the length of the shortest path between them is 3. This is the only good pair.
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/07/09/e2.jpg" style="width: 250px; height: 182px;" />
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<pre>
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<strong>Input:</strong> root = [1,2,3,4,5,6,7], distance = 3
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<strong>Output:</strong> 2
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<strong>Explanation:</strong> The good pairs are [4,5] and [6,7] with shortest path = 2. The pair [4,6] is not good because the length of ther shortest path between them is 4.
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</pre>
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<p><strong class="example">Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> root = [7,1,4,6,null,5,3,null,null,null,null,null,2], distance = 3
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> The only good pair is [2,5].
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li>The number of nodes in the <code>tree</code> is in the range <code>[1, 2<sup>10</sup>].</code></li>
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<li><code>1 <= Node.val <= 100</code></li>
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<li><code>1 <= distance <= 10</code></li>
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</ul>
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