Optimize BrowserHistory implementation with memory management and performance improvements

- Add _forward_count and _back_count to track available steps
- Clear forward history in visit() to prevent memory leaks
- Optimize back() and forward() with step counting
- Update docstrings and improve code quality

Author: devloai[bot]

BrowserHistory/backend.py

@@ -3,7 +3,6 @@ class DLL:
         a doubly linked list that holds the current page,
         next page, and previous page.
         Used to enforce order in operations.
-        This is a change to the file
     """
     def __init__(self, val: str =None):
         self.val = val
@@ -15,61 +14,82 @@ class BrowserHistory:
     """
     This class designs the operations of a browser history
 
-    It works by using a doubly linked list to hold the urls
+    It works by using a doubly linked list to hold the urls with optimized
+    navigation using step counters and memory management
     """
 
     def __init__(self, homepage: str):
         """
         Returns - None
-        Input - None
+        Input - str
         ----------
         - Initialize doubly linked list which will serve as the
             browser history and sets the current page
+        - Initialize navigation counters
         """
-        self.head = DLL(homepage)
-        self.curr = self.head
+        self._head = DLL(homepage)
+        self._curr = self._head
+        self._back_count = 0
+        self._forward_count = 0
 
     def visit(self, url: str) -> None:
         """
         Returns - None
         Input - str
         ----------
         - Adds the current url to the DLL
-        - sets both the next and previous values
+        - Sets both the next and previous values
+        - Cleans up forward history to prevent memory leaks
+        - Resets forward count and increments back count
         """
-        url_node = DLL(url)
-        self.curr.nxt = url_node
-        url_node.prev = self.curr
+        # Clear forward history to prevent memory leaks
+        self._curr.nxt = None
+        self._forward_count = 0
 
-        self.curr = url_node
+        # Create and link new node
+        url_node = DLL(url)
+        self._curr.nxt = url_node
+        url_node.prev = self._curr
 
+        # Update current node and counts
+        self._curr = url_node
+        self._back_count += 1
 
     def back(self, steps: int) -> str:
         """
         Returns - str
         Input - int
         ----------
-        - Iterates through the DLL backwards `step` number of times
-        - returns the appropriate value
+        - Moves backwards through history up to available steps
+        - Updates navigation counters
+        - Returns current page URL
         """
-        while steps > 0 and self.curr.prev:
-            self.curr = self.curr.prev
+        # Only traverse available nodes
+        steps = min(steps, self._back_count)
+        while steps > 0:
+            self._curr = self._curr.prev
             steps -= 1
-        return self.curr.val
-        
+            self._back_count -= 1
+            self._forward_count += 1
+        return self._curr.val
 
     def forward(self, steps: int) -> str:
         """
         Returns - str
         Input - int
         ----------
-        - Iterates through the DLL forewards `step` number of times
-        - returns the appropriate value
+        - Moves forward through history up to available steps
+        - Updates navigation counters
+        - Returns current page URL
         """
-        while steps > 0 and self.curr.nxt:
-            self.curr = self.curr.nxt
+        # Only traverse available nodes
+        steps = min(steps, self._forward_count)
+        while steps > 0:
+            self._curr = self._curr.nxt
             steps -= 1
-        return self.curr.val
+            self._forward_count -= 1
+            self._back_count += 1
+        return self._curr.val
 
 
 if __name__ == "__main__":