made iterators have actually correct underlying data?

Map.hpp

@@ -1,8 +1,10 @@
 // commenting everything out when I commit so all commits my code technically
 // compiles
-#if 0
 #include <algorithm>
 #include <initializer_list>
+#include <iterator>
+#include <optional>
+#include <stdexcept>
 #include <utility>
 #include <vector>
 namespace cs440 {
@@ -13,21 +15,34 @@ private:
   // idx 0 = root
   // left = parent * 2 + 1
   // right = parent * 2 + 2
-  std::vector<ValueType> store;
+  std::vector<std::optional<ValueType>> store;
 
 public:
   // TODO: Iterator functionality
   class Iterator {
+    using underlying = typename std::vector<std::optional<ValueType>>::iterator;
+    underlying store_iter;
+
+  public:
     Iterator() = delete;
-    Iterator(Map &parent, const Key_T &key) {}
+    Iterator(underlying iter) : store_iter{iter} {}
   };
   class ConstIterator {
+    using underlying =
+        typename std::vector<std::optional<ValueType>>::const_iterator;
+    underlying store_iter;
+
+  public:
     ConstIterator() = delete;
-    ConstIterator(Map const &parent, const Key_T &key) {}
+    ConstIterator(underlying iter) : store_iter{iter} {}
   };
   class ReverseIterator {
+    using underlying = typename std::vector<std::optional<ValueType>>::iterator;
+    underlying store_iter;
+
+  public:
     ReverseIterator() = delete;
-    ReverseIterator(Map &parent, const Key_T &key) {}
+    ReverseIterator(underlying store_iter) : store_iter{store_iter} {}
   };
   Map() : store{} {}
   Map(const Map &rhs) : store{rhs.store} {}
@@ -41,8 +56,21 @@ public:
   size_t size() const { return this->store.size(); }
   bool empty() const { return this->store.empty(); }
   // TODO: iterator creation
-  Iterator begin() { return Iterator(*this, ); }
-  Iterator end() { return Iterator(*this, ); }
+  Iterator begin() {
+    Key_T const &start =
+        std::min_element(store.begin(), store.end(),
+                         [](std::optional<ValueType> const &lhs,
+                            std::optional<ValueType> const &rhs) {
+                           if (lhs.has_value() != rhs.has_value()) {
+                             return lhs.has_value();
+                           }
+
+                           return lhs.value().first < rhs.value().first;
+                         })
+            ->first;
+    return Iterator(*this, start);
+  }
+  Iterator end() { std::optional return Iterator(*this, ); }
   ConstIterator begin() const { return ConstIterator(*this, ); }
   ConstIterator end() const { return this->cbegin(); }
   ConstIterator cbegin() const { return this->cend(); }
@@ -86,4 +114,3 @@ public:
   friend bool operator<(const Map &lhs, const Map &rhs) {}
 };
 } // namespace cs440
-#endif