Create 1472-Design-Browser-History.py

python/1472-Design-Browser-History.py

@@ -0,0 +1,57 @@
+"""
+1472. Design Browser History
+"""
+
+
+class DLLNode:
+    def __init__(self, val):
+        self.val = val
+        self.prev = None
+        self.next = None
+
+
+class BrowserHistory:
+    def __init__(self, homepage: str):
+        # initialize head and tail to dummy node
+        self.head = DLLNode(-1)
+        self.tail = DLLNode(-1)
+
+        self.head.next = self.tail
+        self.tail.prev = self.head
+
+        # insert homepage at head node
+        self.insertAtHead(homepage)
+        # update cur pointer to homepage
+        self.cur = self.head.next
+
+    def insertAtHead(self, homepage: str):
+        temp = DLLNode(homepage)
+        temp.next = self.head.next
+        temp.prev = self.head
+
+        self.tail.prev = temp
+        self.head.next = temp
+
+    def visit(self, url: str) -> None:
+        temp = DLLNode(url)
+        # clears forward history
+        temp.next = self.tail
+        temp.prev = self.cur
+        self.tail.prev = temp
+        self.cur.next = temp
+        # update cur pointer to URL
+        self.cur = self.cur.next
+
+    def back(self, steps: int) -> str:
+        i = 0
+        while self.cur.prev != self.head and i < steps:
+            self.cur = self.cur.prev
+            i += 1
+        return self.cur.val
+
+    def forward(self, steps: int) -> str:
+        i = 0
+        while self.cur.next != self.tail and i < steps:
+            self.cur = self.cur.next
+            i += 1
+        return self.cur.val