[Term Entry] C++ Maps: .equal_range()

* Create equal range entry for cpp

* Update equal-range.md

* Update content/cpp/concepts/maps/terms/equal-range/equal-range.md

Co-authored-by: Mamta Wardhani <mamta.wardhani@gmail.com>

* Update content/cpp/concepts/maps/terms/equal-range/equal-range.md

Co-authored-by: Mamta Wardhani <mamta.wardhani@gmail.com>

* Update content/cpp/concepts/maps/terms/equal-range/equal-range.md

Co-authored-by: Mamta Wardhani <mamta.wardhani@gmail.com>

* Update content/cpp/concepts/maps/terms/equal-range/equal-range.md

Co-authored-by: Mamta Wardhani <mamta.wardhani@gmail.com>

* Update content/cpp/concepts/maps/terms/equal-range/equal-range.md

Co-authored-by: Mamta Wardhani <mamta.wardhani@gmail.com>

* Update equal-range.md

* Update equal-range.md

* minor fixes

* fixed formatting

* Minor changes

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Author: arisdelacruz

content/cpp/concepts/maps/terms/equal-range/equal-range.md

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+---
+Title: '.equal_range()'
+Description: 'Returns a pair of iterators defining the range of elements with the given key.'
+Subjects:
+  - 'Code Foundations'
+  - 'Computer Science'
+Tags:
+  - 'Iterators'
+  - 'Map'
+  - 'STL'
+CatalogContent:
+  - 'learn-c-plus-plus'
+  - 'paths/computer-science'
+---
+
+In C++, the **`.equal_range()`** function returns a pair of iterators that define the range of elements matching a given key in an associative container. It is especially useful with `multimap`, where multiple elements can have the same key, allowing developers to retrieve all of them efficiently. In a `map`, where keys are unique, the returned range will contain at most one element.
+
+## Syntax
+
+```pseudo
+mapName.equal_range(key);
+```
+
+**Parameters:**
+
+- `key`: The key value to search for in the map.
+
+**Return value:**
+
+- Returns a `std::pair` of iterators:
+
+  - The first iterator points to the first element equal to the key (or the position where it would be inserted).
+  - The second iterator points to the element just past the last element equal to the key.
+
+## Example
+
+This code uses `.equal_range` to find and print the element(s) with key 3 in a `std::map`:
+
+```cpp
+#include <iostream>
+#include <map>
+
+int main() {
+  std::map<int, std::string> myMap = {
+    {1, "apple"},
+    {2, "banana"},
+    {3, "cherry"},
+    {4, "date"},
+    {5, "elderberry"}
+  };
+
+  // Find the range of elements with key 3
+  auto range = myMap.equal_range(3);
+
+  if (range.first != range.second) {
+    std::cout << "Elements with key 3:" << std::endl;
+      for (auto it = range.first; it != range.second; ++it) {
+        std::cout << it->first << " => " << it->second << std::endl;
+      }
+  } else {
+    std::cout << "No elements with key 3 found." << std::endl;
+  }
+
+  return 0;
+}
+```
+
+The output produced by this code is:
+
+```shell
+Elements with key 3:
+3 => cherry
+```
+
+The code creates a `std::map` of integers to strings and uses the `.equal_range()` function to find the range of elements with the key `3`. Since `std::map` stores unique keys, the resulting range will contain at most one element. If the key exists, the range will include that element; otherwise, the range will be empty.
+
+## Codebyte Example
+
+Run this codebyte to understand how the `.equal_range()` function works:
+
+```codebyte/cpp
+#include <iostream>
+#include <map>
+
+int main() {
+  std::map<int, std::string> fruits = {
+    {1, "apple"},
+    {2, "banana"},
+    {3, "cherry"},
+    {4, "date"}
+  };
+
+  int key = 2;
+  auto range = fruits.equal_range(key);
+
+  if (range.first != range.second) {
+    std::cout << "Element with key " << key << ": ";
+    for (auto it = range.first; it != range.second; ++it) {
+      std::cout << it->first << " => " << it->second << std::endl;
+    }
+  } else {
+      std::cout << "No element with key " << key << " found." << std::endl;
+  }
+
+  return 0;
+}
+```