C++使用For循环创建双链表

我有一个赋值，需要从用户那里获取一个输入字符串，然后使用字符串中的字符填充一个双链表。这意味着我需要遍历users字符串并生成一个双链接列表。我已经创建了一个for循环，输出可以工作，但我的程序在显示输出后立即崩溃。我总共有2周的C++经验，所以请原谅我的新手错误。在下面查找代码。

#include<cstdlib>
#include<iostream>
#include <string>
using namespace std;
struct node {
    string data;
    node *next;
    node *prev; 
};
string getString() {
    string userString;
    cout << " Please enter a string for reversal: ";
    cin >> userString;
    return userString;  
}
// print forward
void printDataFor(node* head);
// print reverse
void printDataRev(node* tail);   
int main() {
    node* head= new node;
    node* tail= new node;
    node* n;
    string reverse = getString();
    int length = reverse.length();
    // loop to create linked list
    for (int i = 0; i < length - 1; i++) {
        if (head->prev == NULL) {
            n = new node;
            n->data = reverse[i];
            n->prev = NULL;
            head = n;
            tail = n;
        }
        else {
            n = new node;
            n->data = reverse[i];
            n->prev = tail;
            tail->next = n;
            tail = n;
        }
    }
    n = new node;
    n->data = reverse[length-1];
    n->prev = tail;
    tail->next = n;
    tail = n;
    tail->next = NULL;
    // call to print reverse
    printDataRev(tail);
}
// print forward
void printDataFor(node* head) {
    node* temp = head;
    while (temp != NULL) {
        cout << temp->data;
        temp = temp->next;
    }
}
// print reverse
void printDataRev(node* tail) {
    node* temp = tail;
    while (temp != NULL) {
        cout << temp->data;
        temp = temp->prev;
    }
}