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Design Browser History
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| ''' | |
| Explanation: | |
| - history: [leetcode, youtube, facebook, google] | |
| - urlPosition: i | |
| visit: pop out all urls after the urlPosition, append the url to visit and move the urlPosition | |
| - history: [leetcode, youtube, facebook, google], steps = 2 | |
| - urlPosition: i | |
| back and forward --> you don't want to go out of bound because of the steps | |
| TC - O(n) for all functions | |
| SC - O(n) for all functions --> to store the browserHistory | |
| ''' | |
| class BrowserHistory: | |
| def __init__(self, homepage: str): | |
| self.browserHistory = [homepage] | |
| self.urlPosition = 0 | |
| def visit(self, url: str) -> None: | |
| while self.urlPosition < len(self.browserHistory) - 1: | |
| self.browserHistory.pop() | |
| self.browserHistory.append(url) | |
| self.urlPosition += 1 | |
| def back(self, steps: int) -> str: | |
| while self.urlPosition > 0 and steps > 0: | |
| self.urlPosition -= 1 | |
| steps -= 1 | |
| return self.browserHistory[self.urlPosition] | |
| def forward(self, steps: int) -> str: | |
| while self.urlPosition < len(self.browserHistory) - 1 and steps > 0: | |
| self.urlPosition += 1 | |
| steps -= 1 | |
| return self.browserHistory[self.urlPosition] | |
| # Your BrowserHistory object will be instantiated and called as such: | |
| # obj = BrowserHistory(homepage) | |
| # obj.visit(url) | |
| # param_2 = obj.back(steps) | |
| # param_3 = obj.forward(steps) |
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