Method Signatures

Create Browser System

BrowserSystem(int maxTabs)

• Creates a browser system with no open tabs.
• maxTabs specifies the maximum number of tabs that can remain open.

Open a Tab

String openTab(String tabId)

• Opens the tab identified by tabId.
• The newly opened tab becomes the most recently used tab.
• If tabId is already open, do not create another copy. Instead, mark the existing tab as the most recently used tab.
• If maxTabs tabs are already open and a different tab is opened, close the least recently used tab.
• Return the identifier of the tab that was closed.
• Return an empty string if no tab was closed.

Use an Open Tab

boolean useTab(String tabId)

• If the specified tab is open, mark it as the most recently used tab and return true.
• Return false if the specified tab is not open.

Get Open Tabs

List<String> getOpenTabs()

• Return the identifiers of all currently open tabs.
• Return them from the least recently used tab to the most recently used tab.
• Return an empty list when no tabs are open.

LRU Rules

• Opening a new tab makes it the most recently used tab.
• Opening an already open tab makes that tab the most recently used.
• Successfully using an open tab makes it the most recently used.
• When removal is required, close exactly one tab: the tab at the least-recently-used position.
• The number of open tabs must never exceed maxTabs.

Constraints

• 1 ≤ maxTabs ≤ 100
• 1 ≤ tabId.length() ≤ 100
• tabId contains printable characters.
• At most 100,000 method calls will be made after creating the browser system.
• Tab identifier comparisons are case-sensitive.
• tabId is never an empty string.

Examples

Example 1

Example 2