Implement Single-Tab Browser History Navigation

Implement a BrowserSession for a single-tab browser.

APIs

• BrowserSession(homepage) — initialize the session; the current page starts at homepage.
• visit(url) — navigate to url from the current page and clear any forward history.
• back(steps) — move up to steps pages back; if fewer pages exist, move as far as possible. Return the current url after the move.
• forward(steps) — move up to steps pages forward; if fewer pages exist, move as far as possible. Return the current url after the move.
• haveVisited(url) — return whether the session has ever visited url at least once since construction, regardless of whether it currently sits in back/forward history.

Driver contract for this console

In JavaScript, TypeScript, and Python you implement a single function solution(operations, args):

• operations is a list of method-name strings; the first is always "BrowserSession".
• args is a parallel list of argument lists, one per operation.
• Replay the operations against one BrowserSession instance and return a list of results, one per operation: null for the constructor and for visit (which return nothing), the resulting url for back and forward, and the boolean for haveVisited.

The starter code already contains that replay loop, so only the class body is yours to fill in. In Java, C++, and Go you implement the BrowserSession class alone and the harness replays the operations for you.

Edge cases to handle

• steps <= 0 (including negative) must not move the cursor.
• visit must truncate any forward history before appending the new page.
• back and forward past the ends clamp to the oldest and newest page.
• haveVisited is true for every url ever visited (and for the homepage), even after a later visit drops that url from the live forward history.

Examples

operations = ["BrowserSession", "visit", "visit", "visit",
              "back", "back", "forward", "visit",
              "forward", "back", "back"]
args       = [["leetcode.com"], ["google.com"],
              ["facebook.com"], ["youtube.com"], [1], [1], [1],
              ["linkedin.com"], [2], [2], [7]]

-> [null, null, null, null, "facebook.com", "google.com",
    "facebook.com", null, "linkedin.com", "google.com",
    "leetcode.com"]

After visiting google, facebook, and youtube the cursor sits at youtube. back(1) lands on facebook and back(1) again on google, then forward(1) returns to facebook. Visiting linkedin.com there clears the forward history — youtube is gone — so forward(2) clamps to linkedin, back(2) reaches google, and back(7) clamps to the homepage.

operations = ["BrowserSession", "visit", "visit",
              "haveVisited", "haveVisited", "back", "haveVisited"]
args       = [["home.com"], ["a.com"], ["b.com"],
              ["a.com"], ["z.com"], [1], ["b.com"]]

-> [null, null, null, true, false, "a.com", true]

a.com was visited so it reports true, while z.com never was. After back(1) lands on a.com, b.com still reports true: the visited set never shrinks.

Constraints

• The first operation is always BrowserSession(homepage), and the current page always exists.
• Urls are non-empty strings.
• steps may be zero or negative; non-positive steps must not move the cursor.
• back and forward clamp at the oldest and newest page rather than erroring.
• Target O(1) amortized time per operation and O(n) space for n total visits.