Create design-browser-history.py

Author: kamyu104

Python/design-browser-history.py

@@ -0,0 +1,40 @@
+# Time:  ctor  : O(1)
+#        visit : O(n)
+#        back  : O(1)
+#        foward: O(1)
+# Space: O(n)
+
+class BrowserHistory(object):
+
+    def __init__(self, homepage):
+        """
+        :type homepage: str
+        """
+        self.__history = [homepage]
+        self.__curr = 0        
+
+    def visit(self, url):
+        """
+        :type url: str
+        :rtype: None
+        """
+        while len(self.__history) > self.__curr+1:
+            self.__history.pop()
+        self.__history.append(url)
+        self.__curr += 1
+
+    def back(self, steps):
+        """
+        :type steps: int
+        :rtype: str
+        """
+        self.__curr = max(self.__curr-steps, 0)
+        return self.__history[self.__curr]
+
+    def forward(self, steps):
+        """
+        :type steps: int
+        :rtype: str
+        """
+        self.__curr = min(self.__curr+steps, len(self.__history)-1)
+        return self.__history[self.__curr]