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leetcode-cn/problem (English)/查找推荐产品对(English) [find-product-recommendation-pairs].html

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+<p>Table: <code>ProductPurchases</code></p>
+
+<pre>
++-------------+------+
+| Column Name | Type | 
++-------------+------+
+| user_id     | int  |
+| product_id  | int  |
+| quantity    | int  |
++-------------+------+
+(user_id, product_id) is the unique key for this table.
+Each row represents a purchase of a product by a user in a specific quantity.
+</pre>
+
+<p>Table: <code>ProductInfo</code></p>
+
+<pre>
++-------------+---------+
+| Column Name | Type    | 
++-------------+---------+
+| product_id  | int     |
+| category    | varchar |
+| price       | decimal |
++-------------+---------+
+product_id is the primary key for this table.
+Each row assigns a category and price to a product.
+</pre>
+
+<p>Amazon wants to implement the <strong>Customers who bought this also bought...</strong> feature based on <strong>co-purchase patterns</strong>. Write a solution to :</p>
+
+<ol>
+	<li>Identify <strong>distinct</strong> product pairs frequently <strong>purchased together by the same customers</strong> (where <code>product1_id</code> &lt; <code>product2_id</code>)</li>
+	<li>For <strong>each product pair</strong>, determine how many customers purchased <strong>both</strong> products</li>
+</ol>
+
+<p><strong>A product pair </strong>is considered for recommendation <strong>if</strong> <strong>at least</strong> <code>3</code> <strong>different</strong> customers have purchased <strong>both products</strong>.</p>
+
+<p>Return <em>the </em><em>result table ordered by <strong>customer_count</strong> in <strong>descending</strong> order, and in case of a tie, by </em><code>product1_id</code><em> in <strong>ascending</strong> order, and then by </em><code>product2_id</code><em> in <strong>ascending</strong> order</em>.</p>
+
+<p>The result format is in the following example.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong></p>
+
+<p>ProductPurchases table:</p>
+
+<pre class="example-io">
++---------+------------+----------+
+| user_id | product_id | quantity |
++---------+------------+----------+
+| 1       | 101        | 2        |
+| 1       | 102        | 1        |
+| 1       | 103        | 3        |
+| 2       | 101        | 1        |
+| 2       | 102        | 5        |
+| 2       | 104        | 1        |
+| 3       | 101        | 2        |
+| 3       | 103        | 1        |
+| 3       | 105        | 4        |
+| 4       | 101        | 1        |
+| 4       | 102        | 1        |
+| 4       | 103        | 2        |
+| 4       | 104        | 3        |
+| 5       | 102        | 2        |
+| 5       | 104        | 1        |
++---------+------------+----------+
+</pre>
+
+<p>ProductInfo table:</p>
+
+<pre class="example-io">
++------------+-------------+-------+
+| product_id | category    | price |
++------------+-------------+-------+
+| 101        | Electronics | 100   |
+| 102        | Books       | 20    |
+| 103        | Clothing    | 35    |
+| 104        | Kitchen     | 50    |
+| 105        | Sports      | 75    |
++------------+-------------+-------+
+</pre>
+
+<p><strong>Output:</strong></p>
+
+<pre class="example-io">
++-------------+-------------+-------------------+-------------------+----------------+
+| product1_id | product2_id | product1_category | product2_category | customer_count |
++-------------+-------------+-------------------+-------------------+----------------+
+| 101         | 102         | Electronics       | Books             | 3              |
+| 101         | 103         | Electronics       | Clothing          | 3              |
+| 102         | 104         | Books             | Kitchen           | 3              |
++-------------+-------------+-------------------+-------------------+----------------+
+</pre>
+
+<p><strong>Explanation:</strong></p>
+
+<ul>
+	<li><strong>Product pair (101, 102):</strong>
+
+	<ul>
+		<li>Purchased by users 1, 2, and 4 (3 customers)</li>
+		<li>Product 101 is in Electronics category</li>
+		<li>Product 102 is in Books category</li>
+	</ul>
+	</li>
+	<li><strong>Product pair (101, 103):</strong>
+	<ul>
+		<li>Purchased by users 1, 3, and 4 (3 customers)</li>
+		<li>Product 101 is in Electronics category</li>
+		<li>Product 103 is in Clothing category</li>
+	</ul>
+	</li>
+	<li><strong>Product pair (102, 104):</strong>
+	<ul>
+		<li>Purchased by users 2, 4, and 5 (3 customers)</li>
+		<li>Product 102 is in Books category</li>
+		<li>Product 104 is in Kitchen category</li>
+	</ul>
+	</li>
+</ul>
+
+<p>The result is ordered by customer_count in descending order. For pairs with the same customer_count, they are ordered by product1_id and then product2_id in ascending order.</p>
+</div>