题解 | #简单的 Fish Shell#

这道题有坑！！！

输入描述说命令与参数之间用一个空格隔开，但实际上样例中它们不是用空格隔开的！

命令与参数之间的空白是一个编码为-15712的不可见字符，如果用读单词的方式读入命令和参数的话，会把一整行字符串都读进来，导致程序出错。这个bug我找了至少四个小时，用单步调试都没看出来！

如果正常写程序的话，很可能会发现样例过不了。但本题的评测数据中还是用空格分隔命令和参数的，所以就算样例没过，也是能AC本题的。要注意一下格式错误，样例中对空目录使用ls命令没有输出，但实际上需要输出一个空行

#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <list>
struct file {
	std::string _name;
	bool _is_dir;
	file * parent;
	std::list<file *> _sub_file;
	file(std::string name, bool is_dir) {
		_name = name;
		_is_dir = is_dir;
		parent = nullptr;
	}
	~file() {
		std::list<file *>::iterator it;
		for (it = _sub_file.begin(); it != _sub_file.end(); it++) {
			delete *it;
			*it=nullptr;
		}
	}
	void create_file(std::string name, bool is_dir) {
		file * new_file = new file(name, is_dir);
		if (is_dir) {
			new_file->parent = this;
		}
		_sub_file.push_back(new_file);
	}
	void get_list() {
		if (_sub_file.size() == 0) {
            std::cout << std::endl;
			return;
		}
		std::list<file *>::iterator it;
		for (it = _sub_file.begin(); it != _sub_file.end(); it++) {
			std::cout << (*it)->_name;
            if (++it != _sub_file.end()) {
                std::cout << "  ";
            }
            --it;
		}
		std::cout << std::endl;
	}
};
struct System {
	file * root;
	file * cur;
	std::vector<std::string> path;
	System() {
		root = new file("", true);
		path.push_back(root->_name);
		cur = root;
	}
	~System() {
		delete root;
		root=nullptr;
	}
	bool execute(std::string command) {
		std::istringstream in(command);
		std::string instruction;
		std::string argument;
		in >> instruction;
		if (instruction == "ls") {
			cur->get_list();
		} else if (instruction == "pwd") {
			get_path();
		} else if (instruction == "exit") {
			return false;
		} else if (instruction == "touch") {
			in >> argument;
			cur->create_file(argument, false);
		} else if (instruction == "mkdir") {
			in >> argument;
			cur->create_file(argument, true);
		} else if (instruction == "cd") {
			in >> argument;
			if (argument == "..") {
				if (cur->parent != nullptr) {
					cur = cur->parent;
					path.pop_back();
				}
			} else {
				size_t i;
				std::list<file *>::iterator it;
				for (it = cur->_sub_file.begin(); it != cur->_sub_file.end(); it++) {
					if ((*it)->_name == argument) {
						break;
					}
				}
				cur = *it;
				path.push_back((*it)->_name);
			}
		}
		else if (instruction == "echo") {
			std::getline(in, argument);
			if (argument != "") {
				argument = argument.substr(2,argument.size()-3);
			}
			std::cout << argument << std::endl;
		}
		else if (instruction == "rm") {
			in >> argument;
			std::list<file *>::iterator it;
			for (it = cur->_sub_file.begin(); it != cur->_sub_file.end(); it++) {
				if ((*it)->_name == argument) {
					break;
				}
			}
			cur->_sub_file.erase(it);
		}
		return true;
	}
	void get_path() {
		std::cout << "/";
		for (size_t i = 1; i < path.size() - 1; i++) {
			std::cout << path[i] << "/";
		}
		std::cout << path[path.size() - 1];
		std::cout << std::endl;
	}
};
int main() {
	System system;
	std::string cmd;
	while (std::getline(std::cin, cmd)) {
		if (!system.execute(cmd)) {
			break;
		}
	}
	return 0;
}