Design Browser History

class NavigationHistory {
    vector<string> history;
    int currentIdx, lastIdx;
public:
    NavigationHistory(string startPage) {
        history.push_back(startPage);
        currentIdx = 0;
        lastIdx = 0;
    }
    
    void visit(string url) {
        currentIdx += 1;
        if (history.size() > currentIdx) {
            history[currentIdx] = url;
        } else {
            history.push_back(url);
        }
        lastIdx = currentIdx;
    }
    
    string back(int steps) {
        currentIdx = max(0, currentIdx - steps);
        return history[currentIdx];
    }
    
    string forward(int steps) {
        currentIdx = min(lastIdx, currentIdx + steps);
        return history[currentIdx];
    }
};

The problem requires defining a simple browser history navigator in C++, where users can visit new pages and navigate forwards or backwards within their browsing history.

The implemented solution, NavigationHistory, uses a vector<string> to store URLs of the sites visited. Two pointer integers, currentIdx and lastIdx, track the current position and the furthest page visited, respectively. Here's a breakdown of how the class functions:

• Upon initialization with a startPage, the history vector includes this page, and both indices currentIdx and lastIdx are set to 0, pointing to the starting page.

• The visit method allows navigation to a new URL. The current index increments to point to the new page location. If this index exceeds the current length of the history vector, the URL is appended to the history. The lastIdx updates to reflect the most recent page.

• The back method enables backward navigation by a given number of steps. It adjusts the currentIdx to ensure it doesn’t fall below zero (which would be out of history bounds), then returns the URL at the new current index.

• The forward method manages forward navigation, checking that currentIdx does not exceed lastIdx. It adjusts the currentIdx appropriately and returns the URL of that position.

This solution ensures efficient tracking and accessing of navigation history, providing basic functionalities similar to web browser history mechanisms. Ensure robust testing, particularly for edge cases like attempting to go back or forward beyond the bounds of the history list.

class WebNavigation {
    ArrayList<String> history;
    int current, end;

    public WebNavigation(String startPage) {
        history = new ArrayList<String>(Arrays.asList(startPage));
        current = 0; 
        end = 0;
    }
    
    public void visit(String page) {
        current += 1;
        if (history.size() > current) {
            history.set(current, page);
        } else {
            history.add(page);
        }
        end = current;
    }
    
    public String back(int steps) {
        current = Math.max(0, current - steps);
        return history.get(current);
    }
    
    public String forward(int steps) {
        current = Math.min(end, current + steps);
        return history.get(current);
    }
}

This solution describes the implementation of a browser history feature using Java, where a user can navigate through their web history either back or forward. The class WebNavigation maintains the user’s browsing history and provides methods to navigate through this history conveniently.

• The primary components declared in the WebNavigation class are:

  • history: an ArrayList that stores the URL of web pages visited.
  • current: an integer index pointing to the current page in the history.
  • end: an integer marking the end of the history list after the latest visit or deletion of forward history.

• On initializing the WebNavigation object with a starting page, the history ArrayList is initialized with the start page, and both current and end are set to 0.

• The visit method allows adding a new page to the browser history:

  • It first increments the current.
  • If the current index is less than the size of the history, it replaces the existing entry; otherwise, it adds the new page to the list.
  • It updates end to the new current, effectively erasing any forward history.

• The back function takes steps as an argument and moves the current index backwards without going below 0, ensuring the user doesn’t navigate back past the beginning of history. It then returns the page at the new current.

• Similarly, the forward function takes steps as an argument and advances the current index forward, capped by the end index which ensures the user cannot navigate forward past their most recently visited page.

Overall, this class provides a structured way to handle browsing history similar to typical web browsers, allowing users to go back and forward through their history based on their navigation actions.

var WebNavigation = function(startPage) {
    this.pages = [startPage];
    this.currentIndex = 0;
    this.maxIndex = 0;
};

WebNavigation.prototype.goTo = function(page) {
    this.currentIndex++;
    if (this.pages.length > this.currentIndex) {
        this.pages[this.currentIndex] = page;
    } else {
        this.pages.push(page);
    }
    this.maxIndex = this.currentIndex;
};

WebNavigation.prototype.goBack = function(steps) {
    this.currentIndex = Math.max(0, this.currentIndex - steps);
    return this.pages[this.currentIndex];
};

WebNavigation.prototype.goForward = function(steps) {
    this.currentIndex = Math.min(this.maxIndex, this.currentIndex + steps);
    return this.pages[this.currentIndex];
};

This JavaScript code implements a simple Web Navigation system where a user can navigate through their browser history, similar to how typical web browsers handle tab history navigation.

• Initialize the browser history with:

  • WebNavigation(startPage): Initializes the navigation system starting at startPage. This function sets up the tracking for pages visited and the current index in the browsing history.

• Navigate to a new webpage:

  • goTo(page): Directs the browser to a new page. This method increments the current index, updates or adds the new page to the history, and adjusts the maximum index reached in the history.

• Move backward through your browser history:

  • goBack(steps): Moves back a certain number of steps in the browser history. The function uses Math.max to prevent the index from going below 0.

• Move forward through your browser history:

  • goForward(steps): Moves forward a number of steps in the browser history. It uses Math.min to ensure the index does not exceed the furthest page visited.

Both goBack(steps) and goForward(steps) return the webpage at the current index after the operation, which allows the user to see the page they navigated to.

class BrowserHistory:
    def __init__(self, homepage: str):
        self.history = [homepage]
        self.current, self.end = 0, 0

    def visit(self, url: str) -> None:
        self.current += 1
        if len(self.history) > self.current:
            self.history[self.current] = url
        else:
            self.history.append(url)
        self.end = self.current

    def back(self, steps: int) -> str:
        self.current = max(0, self.current - steps)
        return self.history[self.current]

    def forward(self, steps: int) -> str:
        self.current = min(self.end, self.current + steps)
        return self.history[self.current]

The provided Python solution involves simulating a simplified browser history with three primary functions: visit, back, and forward. Here's how each function operates:

• Initialization (__init__):

  • Initiate with the homepage setting the starting page of the browser history.

• visit (Visiting a new URL):

  • Increments the current index and updates/adds the URL to the history list. Also resets the end point to the current index, effectively removing forward history after a new visit.

• back (Navigating backwards):

  • Decrements the current index by a given number of steps but does not go below zero. Returns the URL at the adjusted index.

• forward (Navigating forwards):

  • Increments the current index bounded by the end index and returns the URL at the new index.

This basic browser history mechanism effectively uses Python lists to manage URLs and simulate browsing forward and backward through previously visited sites based on user actions.