added syntax, example & codebyte for erase() function

Author: Kimberleyieshaa

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

@@ -0,0 +1,106 @@
+---
+Title: 'erase()'
+Description: 'removes elements from an unordered set'
+Subjects: 
+    - 'Computer Science'
+Tags: 
+    - 'Methods'
+    - 'unordered-sets'
+CatalogContent: 
+    - 'learn-C++'
+    - 'paths/computer-science'
+---
+
+# 'C++ Unordered-sets: erase()'
+
+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.
+Only iterators pointing to erased elements are invalidated; all others remain valid.
+
+## Syntax
+
+Erase by Key
+```
+size_t erase(const Key& key);
+```
+
+Erase by Iterator
+```
+iterator erase(const_iterator pos);
+```
+
+Erase a Range of Iterators
+```
+iterator erase(const_iterator first, const_iterator last);
+```
+
+Erase by Key: Removes all elements matching `key` (in an `unordered_set`, that's at most one). Returns the number of elements removed.
+
+Erase by Iterator: Removes the element at `pos`. Returns an iterator to the element that followed the erased one.
+
+Erase a Range of Iterators: Removes all elements in the half-open range `[first, last]`. Returns an iterator to the element that followed the last removed one.
+
+## Example
+
+```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 << " "; // expected output: 5
+    }
+}
+```
+## Codebyte
+
+The following example creates an `unordered_set<int>`, then demonstrates all three `erase()` overloads:  
+* Erasing by key  
+* Erasing by iterators  
+* Erasing by iterator range  
+
+```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);  
+    // set is now {1, 2, 4, 5}
+
+    // 2. Erase by iterator
+    auto it = s.find(4);
+    if (it != s.end()) {
+        s.erase(it);
+    }
+    // set is now {1, 2, 5}
+
+    // 3. Erase by iterator range
+    auto first = s.begin();
+    auto last = s.end();
+    // this removes everything in the set
+    s.erase(first, last);
+
+    // set is now empty
+
+    return 0;
+}
+```