feat: add solutions to lc problems: No.2978,2979

solution/2900-2999/2978.Symmetric Coordinates/README.md

@@ -0,0 +1,93 @@
+# [2978. Symmetric Coordinates](https://leetcode.cn/problems/symmetric-coordinates)
+
+[English Version](/solution/2900-2999/2978.Symmetric%20Coordinates/README_EN.md)
+
+## 题目描述
+
+<!-- 这里写题目描述 -->
+
+<p>Table: <font face="monospace"><code>Pairs</code></font></p>
+
+<pre>
++-------------+------+
+| Column Name | Type |
++-------------+------+
+| X           | int  |
+| Y           | int  |
++-------------+------+
+Each row includes X and Y, where both are integers. Table may contain duplicate values.
+</pre>
+
+<p>Two coordindates <code>(X1, Y1)</code> and <code>(X2, Y2)</code> are said to be <strong>symmetric</strong> coordintes if <code>X1 == Y2</code> and <code>X2 == Y1</code>.</p>
+
+<p>Write a solution that outputs, among all these <strong>symmetric</strong> <strong>coordintes</strong>, only those <strong>unique</strong> coordinates that satisfy the condition <code>X1 &lt;= Y1</code>.</p>
+
+<p>Return <em>the result table ordered by </em><code>X</code> <em>and </em> <code>Y</code> <em>(respectively)</em> <em>in <strong>ascending order</strong></em>.</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> 
+Coordinates table:
++----+----+
+| X  | Y  |
++----+----+
+| 20 | 20 |
+| 20 | 20 |
+| 20 | 21 |
+| 23 | 22 |
+| 22 | 23 |
+| 21 | 20 |
++----+----+
+<strong>Output:</strong> 
++----+----+
+| x  | y  |
++----+----+
+| 20 | 20 |
+| 20 | 21 |
+| 22 | 23 |
++----+----+
+<strong>Explanation:</strong> 
+- (20, 20) and (20, 20) are symmetric coordinates because, X1 == Y2 and X2 == Y1. This results in displaying (20, 20) as a distinctive coordinates.
+- (20, 21) and (21, 20) are symmetric coordinates because, X1 == Y2 and X2 == Y1. However, only (20, 21) will be displayed because X1 &lt;= Y1.
+- (23, 22) and (22, 23) are symmetric coordinates because, X1 == Y2 and X2 == Y1. However, only (22, 23) will be displayed because X1 &lt;= Y1.
+The output table is sorted by X and Y in ascending order.
+</pre>
+
+## 解法
+
+<!-- 这里可写通用的实现逻辑 -->
+
+**方法一：窗口函数 + 自连接**
+
+我们可以使用窗口函数 `ROW_NUMBER()` 来为每一行添加一个自增的序号，然后再自连接两张表，连接条件为 `p1.x = p2.y AND p1.y = p2.x AND p1.x <= p1.y AND p1.id != p2.id`，最后再排序去重即可。
+
+<!-- tabs:start -->
+
+### **SQL**
+
+<!-- 这里可写当前语言的特殊实现逻辑 -->
+
+```sql
+# Write your MySQL query statement below
+WITH
+    P AS (
+        SELECT
+            ROW_NUMBER() OVER () AS id,
+            x,
+            y
+        FROM Coordinates
+    )
+SELECT DISTINCT
+    p1.x,
+    p1.y
+FROM
+    P AS p1
+    JOIN P AS p2 ON p1.x = p2.y AND p1.y = p2.x AND p1.x <= p1.y AND p1.id != p2.id
+ORDER BY 1, 2;
+```
+
+<!-- tabs:end -->

solution/2900-2999/2978.Symmetric Coordinates/README_EN.md

@@ -0,0 +1,87 @@
+# [2978. Symmetric Coordinates](https://leetcode.com/problems/symmetric-coordinates)
+
+[中文文档](/solution/2900-2999/2978.Symmetric%20Coordinates/README.md)
+
+## Description
+
+<p>Table: <font face="monospace"><code>Pairs</code></font></p>
+
+<pre>
++-------------+------+
+| Column Name | Type |
++-------------+------+
+| X           | int  |
+| Y           | int  |
++-------------+------+
+Each row includes X and Y, where both are integers. Table may contain duplicate values.
+</pre>
+
+<p>Two coordindates <code>(X1, Y1)</code> and <code>(X2, Y2)</code> are said to be <strong>symmetric</strong> coordintes if <code>X1 == Y2</code> and <code>X2 == Y1</code>.</p>
+
+<p>Write a solution that outputs, among all these <strong>symmetric</strong> <strong>coordintes</strong>, only those <strong>unique</strong> coordinates that satisfy the condition <code>X1 &lt;= Y1</code>.</p>
+
+<p>Return <em>the result table ordered by </em><code>X</code> <em>and </em> <code>Y</code> <em>(respectively)</em> <em>in <strong>ascending order</strong></em>.</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> 
+Coordinates table:
++----+----+
+| X  | Y  |
++----+----+
+| 20 | 20 |
+| 20 | 20 |
+| 20 | 21 |
+| 23 | 22 |
+| 22 | 23 |
+| 21 | 20 |
++----+----+
+<strong>Output:</strong> 
++----+----+
+| x  | y  |
++----+----+
+| 20 | 20 |
+| 20 | 21 |
+| 22 | 23 |
++----+----+
+<strong>Explanation:</strong> 
+- (20, 20) and (20, 20) are symmetric coordinates because, X1 == Y2 and X2 == Y1. This results in displaying (20, 20) as a distinctive coordinates.
+- (20, 21) and (21, 20) are symmetric coordinates because, X1 == Y2 and X2 == Y1. However, only (20, 21) will be displayed because X1 &lt;= Y1.
+- (23, 22) and (22, 23) are symmetric coordinates because, X1 == Y2 and X2 == Y1. However, only (22, 23) will be displayed because X1 &lt;= Y1.
+The output table is sorted by X and Y in ascending order.
+</pre>
+
+## Solutions
+
+**Solution 1: Window Function + Self Join**
+
+We can use the window function `ROW_NUMBER()` to add an auto-incrementing sequence number to each row. Then, we perform a self join on the two tables, with the join conditions being `p1.x = p2.y AND p1.y = p2.x AND p1.x <= p1.y AND p1.id != p2.id`. Finally, we sort and remove duplicates.
+
+<!-- tabs:start -->
+
+### **SQL**
+
+```sql
+# Write your MySQL query statement below
+WITH
+    P AS (
+        SELECT
+            ROW_NUMBER() OVER () AS id,
+            x,
+            y
+        FROM Coordinates
+    )
+SELECT DISTINCT
+    p1.x,
+    p1.y
+FROM
+    P AS p1
+    JOIN P AS p2 ON p1.x = p2.y AND p1.y = p2.x AND p1.x <= p1.y AND p1.id != p2.id
+ORDER BY 1, 2;
+```
+
+<!-- tabs:end -->

solution/2900-2999/2978.Symmetric Coordinates/Solution.sql

@@ -0,0 +1,16 @@
+# Write your MySQL query statement below
+WITH
+    P AS (
+        SELECT
+            ROW_NUMBER() OVER () AS id,
+            x,
+            y
+        FROM Coordinates
+    )
+SELECT DISTINCT
+    p1.x,
+    p1.y
+FROM
+    P AS p1
+    JOIN P AS p2 ON p1.x = p2.y AND p1.y = p2.x AND p1.x <= p1.y AND p1.id != p2.id
+ORDER BY 1, 2;

solution/2900-2999/2979.Most Expensive Item That Can Not Be Bought/README.md

@@ -0,0 +1,118 @@
+# [2979. Most Expensive Item That Can Not Be Bought](https://leetcode.cn/problems/most-expensive-item-that-can-not-be-bought)
+
+[English Version](/solution/2900-2999/2979.Most%20Expensive%20Item%20That%20Can%20Not%20Be%20Bought/README_EN.md)
+
+## 题目描述
+
+<!-- 这里写题目描述 -->
+
+<p>You are given two <strong>distinct</strong> <strong>prime</strong> numbers <code>primeOne</code> and <code>primeTwo</code>.</p>
+
+<p>Alice and Bob are visiting a market. The market has an <strong>infinite</strong> number of items, for <strong>any</strong> positive integer <code>x</code> there exists an item whose price is <code>x</code>. Alice wants to buy some items from the market to gift to Bob. She has an <strong>infinite</strong> number of coins in the denomination <code>primeOne</code> and <code>primeTwo</code>. She wants to know the <strong>most expensive</strong> item she can <strong>not</strong> buy to gift to Bob.</p>
+
+<p>Return <em>the price of the <strong>most expensive</strong> item which Alice can not gift to Bob</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> primeOne = 2, primeTwo = 5
+<strong>Output:</strong> 3
+<strong>Explanation:</strong> The prices of items which cannot be bought are [1,3]. It can be shown that all items with a price greater than 3 can be bought using a combination of coins of denominations 2 and 5.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> primeOne = 5, primeTwo = 7
+<strong>Output:</strong> 23
+<strong>Explanation:</strong> The prices of items which cannot be bought are [1,2,3,4,6,8,9,11,13,16,18,23]. It can be shown that all items with a price greater than 23 can be bought.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt; primeOne, primeTwo &lt; 10<sup>4</sup></code></li>
+	<li><code>primeOne</code>, <code>primeTwo</code> are prime numbers.</li>
+	<li><code>primeOne * primeTwo &lt; 10<sup>5</sup></code></li>
+</ul>
+
+## 解法
+
+<!-- 这里可写通用的实现逻辑 -->
+
+**方法一：Chicken McNugget 定理**
+
+根据 Chicken McNugget 定理，两个互质的正整数 $a$ 和 $b$，最大不能表示的数为 $ab - a - b$。
+
+时间复杂度 $O(1)$，空间复杂度 $O(1)$。
+
+<!-- tabs:start -->
+
+### **Python3**
+
+<!-- 这里可写当前语言的特殊实现逻辑 -->
+
+```python
+class Solution:
+    def mostExpensiveItem(self, primeOne: int, primeTwo: int) -> int:
+        return primeOne * primeTwo - primeOne - primeTwo
+```
+
+### **Java**
+
+<!-- 这里可写当前语言的特殊实现逻辑 -->
+
+```java
+class Solution {
+    public int mostExpensiveItem(int primeOne, int primeTwo) {
+        return primeOne * primeTwo - primeOne - primeTwo;
+    }
+}
+```
+
+### **C++**
+
+```cpp
+class Solution {
+public:
+    int mostExpensiveItem(int primeOne, int primeTwo) {
+        return primeOne * primeTwo - primeOne - primeTwo;
+    }
+};
+```
+
+### **Go**
+
+```go
+func mostExpensiveItem(primeOne int, primeTwo int) int {
+	return primeOne*primeTwo - primeOne - primeTwo
+}
+```
+
+### **TypeScript**
+
+```ts
+function mostExpensiveItem(primeOne: number, primeTwo: number): number {
+    return primeOne * primeTwo - primeOne - primeTwo;
+}
+```
+
+### **Rust**
+
+```rust
+impl Solution {
+    pub fn most_expensive_item(prime_one: i32, prime_two: i32) -> i32 {
+        prime_one * prime_two - prime_one - prime_two
+    }
+}
+```
+
+### **...**
+
+```
+
+```
+
+<!-- tabs:end -->