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74 lines
2.6 KiB
HTML
74 lines
2.6 KiB
HTML
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<p>如果一棵二叉树满足下述几个条件，则可以称为 <strong>奇偶树</strong> ：</p>
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<ul>
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<li>二叉树根节点所在层下标为 <code>0</code> ，根的子节点所在层下标为 <code>1</code> ，根的孙节点所在层下标为 <code>2</code> ，依此类推。</li>
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<li><strong>偶数下标</strong> 层上的所有节点的值都是 <strong>奇</strong> 整数，从左到右按顺序 <strong>严格递增</strong></li>
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<li><strong>奇数下标</strong> 层上的所有节点的值都是 <strong>偶</strong> 整数，从左到右按顺序 <strong>严格递减</strong></li>
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</ul>
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<p>给你二叉树的根节点，如果二叉树为 <strong>奇偶树 </strong>，则返回 <code>true</code> ，否则返回 <code>false</code> 。</p>
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<p> </p>
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<p><strong>示例 1：</strong></p>
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<p><strong><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/10/04/sample_1_1966.png" style="height: 229px; width: 362px;" /></strong></p>
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<pre>
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<strong>输入：</strong>root = [1,10,4,3,null,7,9,12,8,6,null,null,2]
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<strong>输出：</strong>true
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<strong>解释：</strong>每一层的节点值分别是：
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0 层：[1]
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1 层：[10,4]
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2 层：[3,7,9]
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3 层：[12,8,6,2]
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由于 0 层和 2 层上的节点值都是奇数且严格递增，而 1 层和 3 层上的节点值都是偶数且严格递减，因此这是一棵奇偶树。
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</pre>
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<p><strong>示例 2：</strong></p>
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<p><strong><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/10/04/sample_2_1966.png" style="height: 167px; width: 363px;" /></strong></p>
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<pre>
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<strong>输入：</strong>root = [5,4,2,3,3,7]
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<strong>输出：</strong>false
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<strong>解释：</strong>每一层的节点值分别是：
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0 层：[5]
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1 层：[4,2]
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2 层：[3,3,7]
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2 层上的节点值不满足严格递增的条件，所以这不是一棵奇偶树。
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</pre>
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<p><strong>示例 3：</strong></p>
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<p><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/10/04/sample_1_333_1966.png" style="height: 167px; width: 363px;" /></p>
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<pre>
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<strong>输入：</strong>root = [5,9,1,3,5,7]
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<strong>输出：</strong>false
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<strong>解释：</strong>1 层上的节点值应为偶数。
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</pre>
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<p><strong>示例 4：</strong></p>
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<pre>
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<strong>输入：</strong>root = [1]
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<strong>输出：</strong>true
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</pre>
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<p><strong>示例 5：</strong></p>
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<pre>
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<strong>输入：</strong>root = [11,8,6,1,3,9,11,30,20,18,16,12,10,4,2,17]
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<strong>输出：</strong>true
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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>树中节点数在范围 <code>[1, 10<sup>5</sup>]</code> 内</li>
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<li><code>1 <= Node.val <= 10<sup>6</sup></code></li>
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</ul>
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