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80 lines
2.2 KiB
HTML
80 lines
2.2 KiB
HTML
<p>Table: <code>Tree</code></p>
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<pre>
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+-------------+------+
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| Column Name | Type |
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+-------------+------+
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| id | int |
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| p_id | int |
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+-------------+------+
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id is the primary key column for this table.
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Each row of this table contains information about the id of a node and the id of its parent node in a tree.
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The given structure is always a valid tree.
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</pre>
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<p> </p>
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<p>Each node in the tree can be one of three types:</p>
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<ul>
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<li><strong>"Leaf"</strong>: if the node is a leaf node.</li>
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<li><strong>"Root"</strong>: if the node is the root of the tree.</li>
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<li><strong>"Inner"</strong>: If the node is neither a leaf node nor a root node.</li>
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</ul>
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<p>Write an SQL query to report the type of each node in the tree.</p>
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<p>Return the result table <strong>ordered</strong> by <code>id</code> <strong>in ascending order</strong>.</p>
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<p>The query result format is in the following example.</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/2021/10/22/tree1.jpg" style="width: 304px; height: 224px;" />
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<pre>
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<strong>Input:</strong>
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Tree table:
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+----+------+
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| id | p_id |
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+----+------+
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| 1 | null |
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| 2 | 1 |
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| 3 | 1 |
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| 4 | 2 |
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| 5 | 2 |
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+----+------+
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<strong>Output:</strong>
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+----+-------+
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| id | type |
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+----+-------+
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| 1 | Root |
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| 2 | Inner |
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| 3 | Leaf |
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| 4 | Leaf |
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| 5 | Leaf |
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+----+-------+
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<strong>Explanation:</strong>
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Node 1 is the root node because its parent node is null and it has child nodes 2 and 3.
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Node 2 is an inner node because it has parent node 1 and child node 4 and 5.
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Nodes 3, 4, and 5 are leaf nodes because they have parent nodes and they do not have child nodes.
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</pre>
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<p><strong>Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/10/22/tree2.jpg" style="width: 64px; height: 65px;" />
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<pre>
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<strong>Input:</strong>
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Tree table:
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+----+------+
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| id | p_id |
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+----+------+
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| 1 | null |
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+----+------+
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<strong>Output:</strong>
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+----+-------+
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| id | type |
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+----+-------+
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| 1 | Root |
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+----+-------+
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<strong>Explanation:</strong> If there is only one node on the tree, you only need to output its root attributes.
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</pre>
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