只用鏈表不用類不用algorithm實現大數加減

以下是使用链表实现大数加减的示例代码，其中使用两个链表分别存储两个大数，通过遍历链表进行相应的运算，最终得到结果：

#include <iostream>
using namespace std;

struct ListNode
{
    int val;
    ListNode* next;
    ListNode(int x) : val(x), next(NULL) {}
};

ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) 
{
    ListNode* p1 = l1;
    ListNode* p2 = l2;
    ListNode* res = new ListNode(0);
    ListNode* p3 = res;
    int carry = 0;
    while (p1 != NULL || p2 != NULL || carry != 0)
    {
        int sum = (p1 == NULL ? 0 : p1->val) + (p2 == NULL ? 0 : p2->val) + carry;
        carry = sum / 10;
        p3->next = new ListNode(sum % 10);
        p3 = p3->next;
        p1 = p1 == NULL ? NULL : p1->next;
        p2 = p2 == NULL ? NULL : p2->next;
    }
    return res->next;
}

ListNode* subtractTwoNumbers(ListNode* l1, ListNode* l2) 
{
    ListNode* p1 = l1;
    ListNode* p2 = l2;
    ListNode* res = new ListNode(0);
    ListNode* p3 = res;
    int borrow = 0;
    while (p1 != NULL || p2 != NULL)
    {
        int num1 = p1 == NULL ? 0 : p1->val;
        int num2 = p2 == NULL ? 0 : p2->val;
        int diff = num1 - num2 - borrow;
        if (diff < 0)
        {
            diff = diff + 10;
            borrow = 1;
        }
        else
        {
            borrow = 0;
        }
        p3->next = new ListNode(diff);
        p3 = p3->next;
        p1 = p1 == NULL ? NULL : p1->next;
        p2 = p2 == NULL ? NULL : p2->next;
    }
    return res->next;
}

int main()
{
    // 输入两个大数，以链表形式存储
    ListNode* l1 = new ListNode(2);
    l1->next = new ListNode(4);
    l1->next->next = new ListNode(3);
    
    ListNode* l2 = new ListNode(5);
    l2->next = new ListNode(6);
    l2->next->next = new ListNode(4);

    // 大数加法
    ListNode* sum = addTwoNumbers(l1, l2);
    cout << "Sum: ";
    while (sum != NULL)
    {
        cout << sum->val << " ";
        sum = sum->next;
    }
    cout << endl;

    // 大数减法
    ListNode* diff = subtractTwoNumbers(l1, l2);
    cout << "Difference: ";
    while (diff != NULL)
    {
        cout << diff->val << " ";
        diff = diff->next;
    }
    cout << endl;

    return 0;
}

以上示例代码实现了使用链表进行大数加减的功能，其中addTwoNumbers函数实现了大数加法，subtractTwoNumbers函数实现了大数减法。