added syntax, example & codebyte for erase() function

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

@@ -0,0 +1,117 @@
+---
+Title: 'erase()'
+Description: 'Removes one or more specified elements from the unordered_set.'
+Subjects:
+  - 'Computer Science'
+  - 'Game Development'
+Tags:
+  - 'Methods'
+  - 'Sets'
+CatalogContent: 
+  - 'learn-c-plus-plus'
+  - 'paths/computer-science'
+---
+
+The **`erase()`** function removes elements from an `unordered_set`. It can erase a single element by key, a single element by iterator, or a range of elements using two iterators, and only iterators pointing to erased elements are invalidated while the rest remain valid.
+
+## Syntax
+
+The `erase()` function removes elements from an `unordered_set` in three ways: by key, by iterator, or by a range of iterators:
+
+```pseudo
+set.erase(key);              // erase by key
+set.erase(iterator);         // erase by iterator
+set.erase(first, last);      // erase by range
+```
+
+**Parameters:**
+
+- `key`: A value of the set’s key type. All elements matching this key are removed (at most one since `unordered_set` stores unique keys).
+- `iterator`: An iterator pointing to the element to remove.
+- `first`, `last`: A pair of iterators defining the range to erase. Removes all elements in `[first, last)`.
+
+**Return value:**
+
+- When erasing by key: returns the number of elements removed, as a `size_type`.
+- When erasing by iterator: returns an iterator pointing to the element that follows the erased one.
+- When erasing by range: returns an iterator pointing to the element that follows the last erased element.
+
+## Example 1: Erasing by key, iterator, and range
+
+In this example the program removes elements using all three `erase()` overloads and prints the remaining contents of the `unordered_set`:
+
+```cpp
+#include <iostream>
+#include <unordered_set>
+
+int main() {
+  std::unordered_set<int> numbers = {1, 2, 3, 4, 5};
+
+  // Erase by key
+  numbers.erase(3);
+
+  // Erase by iterator
+  auto it = numbers.find(4);
+  if (it != numbers.end()) {
+    numbers.erase(it);
+  }
+
+  // Erase using a range
+  auto first = numbers.begin();
+  auto last = numbers.find(5);
+  numbers.erase(first, last);
+
+  for (int n : numbers) {
+    std::cout << n << " ";
+  }
+
+  return 0;
+}
+```
+
+The output of this code is:
+
+```shell
+5 2 1
+```
+
+> **Note:** The order and even the elements removed by a range erase depend on the internal bucket ordering of the `unordered_set`, which is not guaranteed. The final printed sequence may vary across systems.
+
+## Codebyte Example
+
+In this example the program demonstrates each `erase()` form and prints the set contents after every removal step:
+
+```codebyte/cpp
+#include <iostream>
+#include <unordered_set>
+
+int main() {
+  std::unordered_set<int> s = {1, 2, 3, 4, 5};
+
+  // 1. Erase by key
+  s.erase(3);
+  std::cout << "After erasing 3: ";
+  for (int v : s) std::cout << v << " ";
+  std::cout << "\n";
+
+  // 2. Erase by iterator
+  auto it = s.find(4);
+  if (it != s.end()) {
+    s.erase(it);
+  }
+  std::cout << "After erasing iterator to 4: ";
+  for (int v : s) std::cout << v << " ";
+  std::cout << "\n";
+
+  // 3. Erase by iterator range
+  auto first = s.begin();
+  auto last = s.end();
+  s.erase(first, last);
+
+  std::cout << "After erasing full range: ";
+  for (int v : s) std::cout << v << " ";
+  std::cout << "(empty)\n";
+
+  return 0;
+}
+```