g1401_1500.s1472_design_browser_history

Class BrowserHistory

java.lang.Object

g1401_1500.s1472_design_browser_history.BrowserHistory

public class BrowserHistory
extends Object

1472 - Design Browser History.

Medium

You have a browser of one tab where you start on the homepage and you can visit another url, get back in the history number of steps or move forward in the history number of steps.

Implement the BrowserHistory class:

• BrowserHistory(string homepage) Initializes the object with the homepage of the browser.
• void visit(string url) Visits url from the current page. It clears up all the forward history.
• string back(int steps) Move steps back in history. If you can only return x steps in the history and steps > x, you will return only x steps. Return the current url after moving back in history at most steps.
• string forward(int steps) Move steps forward in history. If you can only forward x steps in the history and steps > x, you will forward only x steps. Return the current url after forwarding in history at most steps.

Example:

Input: [“BrowserHistory”,“visit”,“visit”,“visit”,“back”,“back”,“forward”,“visit”,“forward”,“back”,“back”] [[“leetcode.com”],[“google.com”],[“facebook.com”],[“youtube.com”],[1],[1],[1],[“linkedin.com”],[2],[2],[7]]

Output: [null,null,null,null,“facebook.com”,“google.com”,“facebook.com”,null,“linkedin.com”,“google.com”,“leetcode.com”]

Explanation:

BrowserHistory browserHistory = new BrowserHistory(“leetcode.com”);

browserHistory.visit(“google.com”); // You are in “leetcode.com”. Visit “google.com”

browserHistory.visit(“facebook.com”); // You are in “google.com”. Visit “facebook.com”

browserHistory.visit(“youtube.com”); // You are in “facebook.com”. Visit “youtube.com”

browserHistory.back(1); // You are in “youtube.com”, move back to “facebook.com” return “facebook.com”

browserHistory.back(1); // You are in “facebook.com”, move back to “google.com” return “google.com”

browserHistory.forward(1); // You are in “google.com”, move forward to “facebook.com” return “facebook.com”

browserHistory.visit(“linkedin.com”); // You are in “facebook.com”. Visit “linkedin.com”

browserHistory.forward(2); // You are in “linkedin.com”, you cannot move forward any steps.

browserHistory.back(2); // You are in “linkedin.com”, move back two steps to “facebook.com” then to “google.com”. return “google.com”

browserHistory.back(7); // You are in “google.com”, you can move back only one step to “leetcode.com”. return “leetcode.com”

Constraints:

• 1 <= homepage.length <= 20
• 1 <= url.length <= 20
• 1 <= steps <= 100
• homepage and url consist of ‘.’ or lower case English letters.
• At most 5000 calls will be made to visit, back, and forward.

Constructor Summary

Constructors

Constructor and Description
BrowserHistory(String homepage)

Method Summary

Modifier and Type	Method and Description
String	back(int steps)
String	forward(int steps)
void	visit(String url)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BrowserHistory

public BrowserHistory(String homepage)

Method Detail

visit

public void visit(String url)

back

public String back(int steps)

forward

public String forward(int steps)