Added medium level Practise Problems in cpp (#412)

* c++ reference documentation added

* added practice questions in cpp

* Added medium level problems in cpp

---------

Co-authored-by: Shubhadip Bhowmik <[email protected]>

docs/day-25/_category_.json

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+{
+    "label": "Day 25",
+    "position": 25,
+    "link": {
+      "type": "generated-index"
+    }
+  }

docs/day-25/medium-level-questions.md

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+---
+sidebar_position: 1
+title: "Medium Level Questions in C++"
+description: "In this tutorial, we will practise medium level practise problems  in C++ with the help of examples."
+sidebar_label: "medium Practise questions"
+slug: medium-practise-question-cpp
+---
+
+
+## Here are 20 medium level C++ questions along with their solutions:
+
+1. Write a program to find the factorial of a number.
+
+    **Input:** 5
+
+    **Output:** The factorial of 5 is 120.
+
+2. Implement a binary search algorithm.
+
+    **Input:** Sorted array: [1, 3, 5, 7, 9], Target element: 7
+
+    **Output:** Element 7 found at index 3.
+
+3. Create a class to represent a bank account with deposit and withdrawal methods.
+
+    **Input:** Account balance: $100, Deposit amount: $50
+
+    **Output:** Account balance after deposit: $150
+
+4. Write a program to reverse a string.
+
+    **Input:** "Hello, World!"
+
+    **Output:** "!dlroW ,olleH"
+
+5. Implement a stack using a linked list.
+
+    **Input:** Push elements: 10, 20, 30
+
+    **Output:** Stack: 30 -> 20 -> 10
+
+6. Create a class to represent a rectangle with methods to calculate area and perimeter.
+
+    **Input:** Length: 5, Width: 3
+
+    **Output:** Area: 15, Perimeter: 16
+
+7. Write a program to check if a number is prime.
+
+    **Input:** 7
+
+    **Output:** 7 is a prime number.
+
+8. Implement a queue using an array.
+
+    **Input:** Enqueue elements: 10, 20, 30
+
+    **Output:** Queue: 10 -> 20 -> 30
+
+9. Create a class to represent a student with methods to calculate average marks.
+
+    **Input:** Marks: [80, 90, 70, 85]
+
+    **Output:** Average marks: 81.25
+
+10. Write a program to find the largest element in an array.
+
+     **Input:** Array: [5, 10, 3, 8, 2]
+
+     **Output:** The largest element is 10.
+
+11. Implement a binary tree data structure.
+
+     **Input:** Insert elements: 10, 5, 15, 3, 7, 12, 20
+
+     **Output:** Tree: 
+                          10
+                         /  \
+                        5    15
+                      / \   / \
+                     3   7 12  20
+
+12. Create a class to represent a car with methods to start and stop the engine.
+
+     **Input:** None
+
+     **Output:** Car engine started. Car engine stopped.
+
+13. Write a program to check if a string is a palindrome.
+
+     **Input:** "racecar"
+
+     **Output:** "racecar" is a palindrome.
+
+14. Implement a hash table data structure.
+
+     **Input:** Insert key-value pairs: ("John", 25), ("Alice", 30), ("Bob", 35)
+
+     **Output:** Hash table: 
+                          Index 0: ("John", 25)
+                          Index 1: ("Alice", 30)
+                          Index 2: ("Bob", 35)
+
+15. Create a class to represent a circle with methods to calculate area and circumference.
+
+     **Input:** Radius: 5
+
+     **Output:** Area: 78.54, Circumference: 31.42
+
+16. Write a program to sort an array using bubble sort.
+
+     **Input:** Array: [5, 2, 8, 1, 9]
+
+     **Output:** Sorted array: [1, 2, 5, 8, 9]
+
+17. Implement a linked list data structure.
+
+     **Input:** Insert elements: 10, 20, 30
+
+     **Output:** Linked list: 10 -> 20 -> 30
+
+18. Create a class to represent a book with methods to get and set the author and title.
+
+     **Input:** Author: "John Doe", Title: "The Book"
+
+     **Output:** Book details: Author: "John Doe", Title: "The Book"
+
+19. Write a program to find the sum of all elements in an array.
+
+     **Input:** Array: [1, 2, 3, 4, 5]
+
+     **Output:** The sum of all elements is 15.
+
+20. Implement a merge sort algorithm.
+
+     **Input:** Array: [5, 2, 8, 1, 9]
+
+     **Output:** Sorted array: [1, 2, 5, 8, 9]
+
+
+
+## **[check solution here](./solution.md "check solution")**
+