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48 lines
2.1 KiB
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<p>Given the <code>root</code> of a binary tree, return <em>the lowest common ancestor of its deepest leaves</em>.</p>
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<p>Recall that:</p>
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<ul>
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<li>The node of a binary tree is a leaf if and only if it has no children</li>
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<li>The depth of the root of the tree is <code>0</code>. if the depth of a node is <code>d</code>, the depth of each of its children is <code>d + 1</code>.</li>
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<li>The lowest common ancestor of a set <code>S</code> of nodes, is the node <code>A</code> with the largest depth such that every node in <code>S</code> is in the subtree with root <code>A</code>.</li>
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</ul>
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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://s3-lc-upload.s3.amazonaws.com/uploads/2018/07/01/sketch1.png" style="width: 600px; height: 510px;" />
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<pre>
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<strong>Input:</strong> root = [3,5,1,6,2,0,8,null,null,7,4]
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<strong>Output:</strong> [2,7,4]
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<strong>Explanation:</strong> We return the node with value 2, colored in yellow in the diagram.
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The nodes coloured in blue are the deepest leaf-nodes of the tree.
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Note that nodes 6, 0, and 8 are also leaf nodes, but the depth of them is 2, but the depth of nodes 7 and 4 is 3.</pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> root = [1]
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<strong>Output:</strong> [1]
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<strong>Explanation:</strong> The root is the deepest node in the tree, and it's the lca of itself.
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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 = [0,1,3,null,2]
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<strong>Output:</strong> [2]
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<strong>Explanation:</strong> The deepest leaf node in the tree is 2, the lca of one node is itself.
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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 tree will be in the range <code>[1, 1000]</code>.</li>
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<li><code>0 <= Node.val <= 1000</code></li>
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<li>The values of the nodes in the tree are <strong>unique</strong>.</li>
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</ul>
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<p> </p>
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<p><strong>Note:</strong> This question is the same as 865: <a href="https://leetcode.com/problems/smallest-subtree-with-all-the-deepest-nodes/" target="_blank">https://leetcode.com/problems/smallest-subtree-with-all-the-deepest-nodes/</a></p>
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