leetcode-problemset/leetcode/problem/rearrange-products-table.html

<p>Table: <code>Products</code></p>

<pre>
+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| product_id  | int     |
| store1      | int     |
| store2      | int     |
| store3      | int     |
+-------------+---------+
product_id is the primary key (column with unique values) for this table.
Each row in this table indicates the product&#39;s price in 3 different stores: store1, store2, and store3.
If the product is not available in a store, the price will be null in that store&#39;s column.
</pre>

<p>&nbsp;</p>

<p>Write a solution to rearrange the <code>Products</code> table so that each row has <code>(product_id, store, price)</code>. If a product is not available in a store, do <strong>not</strong> include a row with that <code>product_id</code> and <code>store</code> combination in the result table.</p>

<p>Return the result table in <strong>any order</strong>.</p>

<p>The result format is in the following example.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> 
Products table:
+------------+--------+--------+--------+
| product_id | store1 | store2 | store3 |
+------------+--------+--------+--------+
| 0          | 95     | 100    | 105    |
| 1          | 70     | null   | 80     |
+------------+--------+--------+--------+
<strong>Output:</strong> 
+------------+--------+-------+
| product_id | store  | price |
+------------+--------+-------+
| 0          | store1 | 95    |
| 0          | store2 | 100   |
| 0          | store3 | 105   |
| 1          | store1 | 70    |
| 1          | store3 | 80    |
+------------+--------+-------+
<strong>Explanation:</strong> 
Product 0 is available in all three stores with prices 95, 100, and 105 respectively.
Product 1 is available in store1 with price 70 and store3 with price 80. The product is not available in store2.
</pre>