c++代码实现以单链表为文件存储结构稳定的直接插入排序。

下面是以单链表为文件存储结构稳定的直接插入排序的C++代码实现：

#include <iostream>
#include <fstream>

using namespace std;

struct Node{
    int data;
    Node *next;
};

void insert(Node *&head, int x){
    Node *p = new Node;
    p->data = x;
    p->next = head;
    head = p;
}

void print(Node *head){
    while(head){
        cout << head->data << " ";
        head = head->next;
    }
    cout << endl;
}

void readFromFile(Node *&head){
    ifstream inFile;
    inFile.open("data.txt");
    if (!inFile) {
        cerr << "Unable to open file data.txt";
        exit(1);
    }

    int x;
    while (inFile >> x) {
        insert(head, x);
    }
    inFile.close();
}

void writeToFile(Node *head){
    ofstream outFile;
    outFile.open("result.txt");
    if (!outFile) {
        cerr << "Unable to open file result.txt";
        exit(1);
    }

    while (head) {
        outFile << head->data << endl;
        head = head->next;
    }
    outFile.close();
}

void insertionSort(Node *&head){
    Node *sortedHead = nullptr; //已排序部分的头结点
    Node *cur = head; //未排序部分的头结点

    while(cur){
        Node *tmp = cur;
        cur = cur->next;

        //将tmp节点插入到已排序部分中
        if(sortedHead == nullptr || tmp->data < sortedHead->data){
            tmp->next = sortedHead;
            sortedHead = tmp;
        }else{
            Node *p = sortedHead;
            while(p->next && tmp->data >= p->next->data){
                p = p->next;
            }
            tmp->next = p->next;
            p->next = tmp;
        }
    }

    head = sortedHead;
}

int main(){
    Node *head = nullptr;
    readFromFile(head);
    print(head);

    insertionSort(head);
    print(head);

    writeToFile(head);
    return 0;
}

其中，`readFromFile`函数从文件中读取数据并创建链表，`writeToFile`函数将排序后的链表写入文件。`insertionSort`函数实现直接插入排序算法，注意要保证算法的稳定性。

完整代码已经实现了单链表的创建、打印、排序和文件读写等操作，你可以直接运行并测试。