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29 lines
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29 lines
1.5 KiB
HTML
<p>Given the <code>root</code> of a binary tree, determine if it is a <em>complete binary tree</em>.</p>
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<p>In a <strong><a href="http://en.wikipedia.org/wiki/Binary_tree#Types_of_binary_trees" target="_blank">complete binary tree</a></strong>, every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between <code>1</code> and <code>2<sup>h</sup></code> nodes inclusive at the last level <code>h</code>.</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/2018/12/15/complete-binary-tree-1.png" style="width: 180px; height: 145px;" />
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<pre>
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<strong>Input:</strong> root = [1,2,3,4,5,6]
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<strong>Output:</strong> true
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<strong>Explanation:</strong> Every level before the last is full (ie. levels with node-values {1} and {2, 3}), and all nodes in the last level ({4, 5, 6}) are as far left as possible.
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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/2018/12/15/complete-binary-tree-2.png" style="width: 200px; height: 145px;" />
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<pre>
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<strong>Input:</strong> root = [1,2,3,4,5,null,7]
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<strong>Output:</strong> false
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<strong>Explanation:</strong> The node with value 7 isn't as far left as possible.
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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>[1, 100]</code>.</li>
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<li><code>1 <= Node.val <= 1000</code></li>
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</ul>
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