写一个利用文件系统实现一个避免死锁算法c++程序

下面是一个简单的利用文件系统实现银行家算法的C++程序示例：

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <vector>
#include <string>

using namespace std;

// 资源分配记录结构体
struct AllocationRecord {
    int process_id; // 进程ID
    vector<int> allocation; // 已分配的资源数量
    vector<int> request; // 请求的资源数量
};

// 文件系统操作类
class FileSystem {
public:
    FileSystem() {
        // 初始化资源总数和可用资源数量
        total_resources = vector<int>{10, 5, 7};
        available_resources = vector<int>{10, 5, 7};
    }

    // 检查资源请求是否满足银行家算法的条件
    bool check_request(const AllocationRecord& record) {
        // 检查请求的资源数量是否超过了该进程所需的最大资源数量
        for (int i = 0; i < total_resources.size(); ++i) {
            if (record.request[i] > (max_resources[record.process_id])[i] - (record.allocation)[i]) {
                return false;
            }
        }

        // 检查请求的资源数量是否超过了系统当前可用的资源数量
        for (int i = 0; i < total_resources.size(); ++i) {
            if (record.request[i] > available_resources[i]) {
                return false;
            }
        }

        return true;
    }

    // 分配资源
    void allocate_resources(const AllocationRecord& record) {
        // 更新已分配资源数量和可用资源数量
        for (int i = 0; i < total_resources.size(); ++i) {
            (allocation_table[record.process_id])[i] += record.request[i];
            available_resources[i] -= record.request[i];
        }
    }

    // 释放资源
    void release_resources(const AllocationRecord& record) {
        // 更新已分配资源数量和可用资源数量
        for (int i = 0; i < total_resources.size(); ++i) {
            (allocation_table[record.process_id])[i] -= record.request[i];
            available_resources[i] += record.request[i];
        }
    }

    // 从文件中读取资源分配记录
    vector<AllocationRecord> read_records(const string& filename) {
        vector<AllocationRecord> records;

        ifstream fin(filename);
        if (fin.fail()) {
            cerr << "Failed to open file " << filename << endl;
            exit(1);
        }

        string line;
        while (getline(fin, line)) {
            AllocationRecord record;
            record.process_id = stoi(line.substr(0, line.find(' ')));
            line = line.substr(line.find(' ') + 1);

            while (line.size() > 0) {
                int num = stoi(line.substr(0, line.find(' ')));
                record.allocation.push_back(num);
                line = line.substr(line.find(' ') + 1);
            }

            getline(fin, line);
            while (line.size() > 0) {
                int num = stoi(line.substr(0, line.find(' ')));
                record.request.push_back(num);
                line = line.substr(line.find(' ') + 1);
            }

            records.push_back(record);
        }

        fin.close();

        return records;
    }

    // 将资源分配记录写入文件
    void write_records(const string& filename, const vector<AllocationRecord>& records) {
        ofstream fout(filename);
        if (fout.fail()) {
            cerr << "Failed to open file " << filename << endl;
            exit(1);
        }

        for (int i = 0; i < records.size(); ++i) {
            fout << records[i].process_id << " ";
            for (int j = 0; j < total_resources.size(); ++j) {
                fout << records[i].allocation[j] << " ";
            }

            fout << endl;

            for (int j = 0; j < total_resources.size(); ++j) {
                fout << records[i].request[j] << " ";
            }

            fout << endl;
        }

        fout.close();
    }

private:
    vector<int> total_resources; // 资源总数
    vector<int> available_resources; // 可用资源数量
    vector<vector<int>> allocation_table; // 已分配资源数量表
    vector<vector<int>> max_resources; // 最大资源数量表
};

int main() {
    FileSystem fs;
    vector<AllocationRecord> records = fs.read_records("records.txt");

    vector<AllocationRecord> waiting_list;

    while (records.size() > 0) {
        // 遍历所有等待的资源请求
        for (int i = 0; i < waiting_list.size(); ++i) {
            if (fs.check_request(waiting_list[i])) {
                // 如果请求满足银行家算法的条件，则分配资源
                fs.allocate_resources(waiting_list[i]);
                records.push_back(waiting_list[i]);
                waiting_list.erase(waiting_list.begin() + i);
            }
        }

        // 遍历所有未完成的资源请求
        for (int i = 0; i < records.size(); ++i) {
            if (fs.check_request(records[i])) {
                // 如果请求满足银行家算法的条件，则分配资源
                fs.allocate_resources(records[i]);
                records.erase(records.begin() + i);
            }
            else {
                // 如果请求不满足银行家算法的条件，则将其加入等待列表
                waiting_list.push_back(records[i]);
                records.erase(records.begin() + i);
            }
        }

        // 定期释放资源
        if (rand() % 5 == 0 && waiting_list.size() == 0) {
            AllocationRecord record;
            record.process_id = rand() % 5;
            for (int i = 0; i < fs.total_resources.size(); ++i) {
                record.request.push_back((fs.allocation_table[record.process_id])[i]);
            }

            fs.release_resources(record);
        }
    }

    fs.write_records("records.txt", records);

    return 0;
}

在这个示例中，我们使用FileSystem类来实现了银行家算法。我们首先从文件中读取资源分配记录，然后按照银行家算法的规则对资源进行分配和释放。同时，我们还定期随机释放一些资源，以确保系统不会一直处于资源短缺状态。最后，我们将更新后的资源分配记录写回文件中。