问指针丢失对前一个节点C++的引用

EN

nextNode = nodePtr->next;
prevNode = nodePtr->prev;
nextNode->prev = prevNode;
prevNode->next = nextNode;
delete(nodePtr);

#include <iostream>
using namespace std;

int main() {

    struct ListNode {
        int value;
        ListNode *next;
        ListNode *prev;
    };

    ListNode *head = nullptr;
    ListNode *newNode = nullptr;
    ListNode *nodePtr = nullptr;
    ListNode *prevPtr = nullptr;
    ListNode *nextNode = nullptr;
    ListNode *prevNode = nullptr;

    char ch = 'q';
    int val;
    int pos;

    do
    {
        cout << "h-delete from position" << endl;
        cout << "i-insert" << endl;
        cout << "p-print" << endl;
        cout << "q-quit" << endl;

        cin >> ch;

        switch (ch) {

        case 'i':

            cout << "inserting ... \n";
            cout << "Enter an integer: ";
            cin >> val;

            newNode = new ListNode;
            newNode->value = val;
            newNode->next = nullptr;

            if (head == nullptr) {
                head = newNode;
            }
            else {
                nodePtr = head;
                prevPtr = nullptr;

                while (nodePtr != nullptr && nodePtr->value < newNode->value) {
                    prevPtr = nodePtr;
                    nodePtr = nodePtr->next;
                }
                if (prevPtr == nullptr) {
                    head = newNode;
                    newNode->next = nodePtr;
                }
                else {
                    prevPtr->next = newNode;
                    newNode->next = nodePtr;
                }

            }
            break;

        case 'p':

            cout << "printing ... \n";
            nodePtr = head;
            while (nodePtr != nullptr) {
                cout << "elem: " << nodePtr->value << endl;
                nodePtr = nodePtr->next;
            }
            break;

        case 'h':
            //FIX
            int findVal;
            cin >> findVal;


            nodePtr = head;
            while (nodePtr->value != findVal) {
                nodePtr = nodePtr->next;
            }
            nextNode = nodePtr->next;
            prevNode = nodePtr->prev;
            nextNode->prev = prevNode;
            prevNode->next = nextNode;
            delete(nodePtr);

            break;

        case 'q':

            cout << "quitting ... \n";
            nodePtr = head;
            while (nodePtr != nullptr) {
                nextNode = nodePtr->next;
                cout << "deleting ... " << nodePtr->value << endl;
                delete nodePtr;
                nodePtr = nextNode;
            }

            break;

        default:
            system("CLS");
            cout << "Invalid character -- Please try again!" << endl;
            break;
        }

    } while (ch != 'q');


    system("pause");
    return 0;
}