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LeetCode 1472: Design Browser History Solution

Master LeetCode problem 1472 (Design Browser History), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

Problem Explanation

Explanation

To solve this problem, we can use a list to keep track of the visited URLs. We also need to maintain an index to represent the current position in the history. When a new URL is visited, we add it to the list and update the index. When moving back or forward in history, we adjust the index accordingly.

Algorithm:

  1. Initialize a list to store visited URLs and an integer index to keep track of the current position in the history.
  2. Initialize the BrowserHistory class with the homepage by adding it to the list and setting the index to 0.
  3. When visiting a new URL, clear all entries after the current index, add the new URL to the list, and update the index.
  4. When moving back in history, decrement the index by the specified number of steps but ensure it stays within bounds.
  5. When moving forward in history, increment the index by the specified number of steps but ensure it stays within bounds.

Time Complexity:

  • Visiting a URL, moving back, or moving forward: O(1)
  • Overall space complexity: O(n), where n is the total number of visited URLs

Solution Code

class BrowserHistory {
    List<String> history;
    int index;

    public BrowserHistory(String homepage) {
        history = new ArrayList<>();
        history.add(homepage);
        index = 0;
    }

    public void visit(String url) {
        while (history.size() > index + 1) {
            history.remove(history.size() - 1);
        }
        history.add(url);
        index++;
    }

    public String back(int steps) {
        index = Math.max(0, index - steps);
        return history.get(index);
    }

    public String forward(int steps) {
        index = Math.min(history.size() - 1, index + steps);
        return history.get(index);
    }
}

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