题目链接

1472. 设计浏览器历史记录

思路

用栈 history 模拟网页的前进后退操作，用栈 temp 来暂时存储后退所退出的网页。

代码

class BrowserHistory{
    Stack<String> history;
    Stack<String> temp;

    public BrowserHistory(String homepage){

        this.history = new Stack<>();
        this.history.push(homepage);
        this.temp = new Stack<>();
    }

    public void visit(String url){

        this.history.push(url);
        this.temp.clear();
    }

    public String back(int steps){

        while(steps > 0 && this.history.size() > 1){
            this.temp.push(this.history.pop());
            steps--;
        }

        return this.history.peek();
    }

    public String forward(int steps){

        while(steps > 0 && this.temp.size() > 0){
            this.history.push(this.temp.pop());
            steps--;
        }

        return this.history.peek();
    }
}