1472. Design Browser History

解題思路

其實就照題目敘述實作即可。

只是 back() 的部分要注意，如果 stack 裡面只剩一個就不要 pop 了，不然連首頁都會不見。

程式碼

class BrowserHistory {
public:
    stack<string> backHistory;
    stack<string> forwardHistory;
    
    BrowserHistory(string homepage) {
        backHistory.push(homepage);
    }
    
    void visit(string url) {
        while (!forwardHistory.empty())
            forwardHistory.pop();
        backHistory.push(url);
    }
    
    string back(int steps) {
        while (steps  && backHistory.size() > 1) {
            forwardHistory.push(backHistory.top());
            backHistory.pop();
            steps--;
        }
        return backHistory.top();
    }
    
    string forward(int steps) {
        while (steps && !forwardHistory.empty()) {
            backHistory.push(forwardHistory.top());
            forwardHistory.pop();
            steps--;
        }
        return backHistory.top();
    }
};