added the backend of the browser history

Author: Xceptions

BrowserHistory/backend.py

@@ -0,0 +1,47 @@
+class DLL:
+    def __init__(self, val: str =None):
+        self.val = val
+        self.nxt = None
+        self.prev = None
+
+
+class BrowserHistory:
+    """
+        This class designs the operations of a
+        broswer history
+    """
+
+    def __init__(self, homepage: str):
+        self.head = DLL(homepage)
+        self.curr = self.head
+        
+    def visit(self, url: str) -> None:
+        url_node = DLL(url)
+        self.curr.nxt = url_node
+        url_node.prev = self.curr
+        
+        self.curr = url_node
+        
+
+    def back(self, steps: int) -> str:
+        while steps > 0 and self.curr.prev:
+            self.curr = self.curr.prev
+            steps -= 1
+        return self.curr.val
+        
+
+    def forward(self, steps: int) -> str:
+        while steps > 0 and self.curr.nxt:
+            self.curr = self.curr.nxt
+            steps -= 1
+        return self.curr.val
+        
+
+if __name__ == "__main__":
+    obj = BrowserHistory("google.com")
+    obj.visit("twitter.com")
+    param_2 = obj.back(1)
+    param_3 = obj.forward(1)
+
+    print(param_2)
+    print(param_3)