在linux环境下编写c++应用程序，设计要求: 1．用户可以为程序指定初始需要访问序列； 2．实现最短寻道和电梯调度两种调度算法； 3.根据用户的选择输出实际的访问序列；

好的，这是一个磁盘调度算法的问题。最短寻道优先(SSTF)和电梯调度算法(Elevator)都是常见的磁盘调度算法。下面是一个简单的实现，解释了如何在Linux环境下编写C++应用程序。

代码如下：

#include <iostream>
#include <queue>
#include <algorithm>
#include <cstdlib>

using namespace std;

// 生成磁盘请求序列
vector<int> generateRequests(int start, int end, int count)
{
    vector<int> requests(count);
    for (int i = 0; i < count; i++) {
        requests[i] = rand() % (end - start + 1) + start;
    }
    return requests;
}

// 最短寻道优先算法
void SSTF(vector<int>& requests, int start)
{
    int head = start;
    int total = 0;
    while (!requests.empty()) {
        int index = 0;
        int minDist = abs(head - requests[0]);
        for (int i = 1; i < requests.size(); i++) {
            int dist = abs(head - requests[i]);
            if (dist < minDist) {
                index = i;
                minDist = dist;
            }
        }
        total += minDist;
        head = requests[index];
        cout << head << " ";
        requests.erase(requests.begin() + index);
    }
    cout << endl;
    cout << "Total seek distance: " << total << endl;
}

// 电梯调度算法
void Elevator(vector<int>& requests, int start)
{
    int head = start;
    int total = 0;
    bool direction = true; // true表示向上，false表示向下
    while (!requests.empty()) {
        if (direction) {    // 向上
            int index = -1;
            int minDist = INT_MAX;
            for (int i = 0; i < requests.size(); i++) {
                if (requests[i] >= head && abs(head - requests[i]) < minDist) {
                    index = i;
                    minDist = abs(head - requests[i]);
                }
            }
            if (index == -1) {  // 如果没有找到，就改变方向
                direction = false;
                continue;
            }
            total += minDist;
            head = requests[index];
            cout << head << " ";
            requests.erase(requests.begin() + index);
        }
        else {  // 向下
            int index = -1;
            int minDist = INT_MAX;
            for (int i = 0; i < requests.size(); i++) {
                if (requests[i] <= head && abs(head - requests[i]) < minDist) {
                    index = i;
                    minDist = abs(head - requests[i]);
                }
            }
            if (index == -1) {  // 如果没有找到，就改变方向
                direction = true;
                continue;
            }
            total += minDist;
            head = requests[index];
            cout << head << " ";
            requests.erase(requests.begin() + index);
        }
    }
    cout << endl;
    cout << "Total seek distance: " << total << endl;
}

int main(int argc, char** argv)
{
    if (argc != 4) {
        cerr << "Usage: " << argv[0] << " start end count" << endl;
        return 1;
    }

    int start = atoi(argv[1]);
    int end = atoi(argv[2]);
    int count = atoi(argv[3]);

    vector<int> requests = generateRequests(start, end, count);
    cout << "Initial requests: ";
    for (int i = 0; i < requests.size(); i++) {
        cout << requests[i] << " ";
    }
    cout << endl;

    cout << "SSTF scheduling: ";
    SSTF(requests, start);

    requests = generateRequests(start, end, count);  // 重新生成请求序列
    cout << "Elevator scheduling: ";
    Elevator(requests, start);

    return 0;
}

这个程序生成随机的磁盘请求序列，然后实现了两种调度算法：最短寻道优先算法和电梯调度算法。用户可以通过命令行参数指定起始磁道号、终止磁道号和请求个数。在输出中，我们会输出实际的访问序列和总寻道距离。