docs: Add C++ unordered_set::clear() term entry (#8030)

Author: Rishabh1925

content/cpp/concepts/unordered-set/terms/clear/clear.md

@@ -0,0 +1,110 @@
+---
+Title: '.clear()'
+Description: 'Removes all elements from the unordered_set, leaving the container with a size of zero.'
+Subjects:
+  - 'Computer Science'
+  - 'Programming'
+Tags:
+  - 'C++'
+  - 'Unordered Set'
+  - 'STL'
+  - 'Containers'
+CatalogContent:
+  - 'learn-c-plus-plus'
+  - 'paths/computer-science'
+---
+
+The **`.clear()`** method is used to remove all elements from an `std::unordered_set`. After calling this method, the set will be empty, and its size will be zero.
+
+The capacity of the set's internal storage (the number of buckets) is typically **not** reduced by `clear()`. The allocated memory for the container's structure often remains intact, although the memory occupied by the individual elements is deallocated.
+
+All iterators, pointers, and references pointing to elements within the set are invalidated after calling `clear()`.
+
+## Syntax
+
+The `.clear()` method is called directly on the `unordered_set` object and takes no arguments.
+
+```cpp
+unordered_set_name.clear();
+```
+
+## Parameters
+
+The method takes no parameters.
+
+## Return Value
+
+The method returns `void` (nothing).
+
+## Example
+
+This example demonstrates using `.clear()` to empty a set and confirms the change by checking the size before and after the operation.
+
+```cpp
+#include <iostream>
+#include <string>
+#include <unordered_set>
+
+int main() {
+  std::unordered_set<std::string> planets = {
+    "Mercury",
+    "Venus",
+    "Earth",
+    "Mars"
+  };
+
+  std::cout << "--- Before clear() ---\n";
+  std::cout << "Size: " << planets.size() << "\n";
+  
+  // Call clear() to remove all elements
+  planets.clear();
+
+  std::cout << "\n--- After clear() ---\n";
+  std::cout << "Size: " << planets.size() << "\n";
+  
+  if (planets.empty()) {
+    std::cout << "The set is now empty.\n";
+  }
+
+  return 0;
+}
+```
+
+Output:
+
+```
+--- Before clear() ---
+Size: 4
+
+--- After clear() ---
+Size: 0
+The set is now empty.
+```
+
+## Codebyte
+
+Use the Codebyte below to practice using `.clear()` on a set of integers.
+
+```cpp
+#include <iostream>
+#include <unordered_set>
+
+int main() {
+  std::unordered_set<int> data_points = {10, 20, 30, 40, 50};
+  
+  // Print initial size
+  std::cout << "Initial size: " << data_points.size() << "\n";
+  
+  // Clear the set
+  data_points.clear();
+  
+  // Print final size
+  std::cout << "Final size: " << data_points.size() << "\n";
+
+  // Attempting to insert a new element (the set is still valid)
+  data_points.insert(999);
+  std::cout << "Size after new insert: " << data_points.size() << "\n";
+
+  return 0;
+}
+```