Web Browser

Implement a web browser with the following methods:

• WebBrowser(String homepage) constructs a new instance of the browser with starting page of homepage.
• visit(String page) visits the site page, clearing all forward history.
• back(int n) goes back n number of steps in history and returns the current page. Note that once you reach the homepage, you stay on that page even if you go back.
• forward(int n) goes forward n number of steps in history and returns the current page. Note that once you reach the most recent page, you stay on that page even if you go forward.

Constraints

• n ≤ 100,000 where n is the number of calls to visit, back and forward.

https://binarysearch.com/problems/Web-Browser

Examples

Example 1

Input

• methods = ['constructor', 'visit', 'visit', 'visit', 'back', 'forward']
• arguments = [['wikipedia.org'], ['google.com'], ['stackoverflow.com'], ['github.com'], [2], [1]]

Output

• answer = [None, None, None, None, 'google.com', 'stackoverflow.com']

Explanation

browser = WebBrowser("wikipedia.org")
browser.visit("google.com")
browser.visit("stackoverflow.com")
browser.visit("github.com")
browser.back(2) == "google.com"
browser.forward(1) == "stackoverflow.com"

Solution