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32 lines
900 B
HTML
32 lines
900 B
HTML
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<p>Given the <code>root</code> of a binary tree, return <em>the bottom-up level order traversal of its nodes' values</em>. (i.e., from left to right, level by level from leaf to root).</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/tree1.jpg" style="width: 277px; height: 302px;" />
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<pre>
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<strong>Input:</strong> root = [3,9,20,null,null,15,7]
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<strong>Output:</strong> [[15,7],[9,20],[3]]
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</pre>
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<p><strong>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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</pre>
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<p><strong>Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> root = []
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<strong>Output:</strong> []
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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 is in the range <code>[0, 2000]</code>.</li>
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<li><code>-1000 <= Node.val <= 1000</code></li>
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</ul>
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