多项式乘法

L1和L2是两个带头结点的单链表表示的多项式，编写算法计算两个多项式的乘积，运算结果仍用单链表进行存储

#include 

using namespace std;

typedef struct LNode {
    int coefficient;    //系数
    int degree; //次数
    struct LNode *next; //下一个结点
} LNode, *LinkedList;

/**
 * 查找计算结果应该插入的位置
 * @param L 链表的头结点指针
 * @param degree 次数
 * @return 插入结点的前一个结点
 */
LinkedList findPre(LinkedList L, int degree) {
    LinkedList pre = L;
    LNode *p = L->next;
    while (p != nullptr) {
        if (p->degree <= degree) {
            break;
        }
        pre = p;
        p = p->next;
    }
    return pre;
}


/**
 * 两个多项式进行乘法运算（多项式的次数按递减排列）
 * @param L1  多项式一
 * @param L2 多项式二
 * @return 计算结果
 */
LinkedList calculate(LinkedList L1, LinkedList L2) {
    // 结果的头结点
    LinkedList head = (LinkedList) malloc(sizeof(LNode));
    head->next = nullptr;
    LNode *p = L1->next;
    while (p != nullptr) {
        LNode *q = L2->next;
        while (q != nullptr) {
            // 暂存结点信息
            LinkedList temp = (LinkedList) malloc(sizeof(LNode));
            // 系数相乘
            temp->coefficient = p->coefficient * q->coefficient;
            // 次数
            temp->degree = p->degree + q->degree;
            temp->next = nullptr;
            // 将temp插入到结果链表中
            LinkedList insertNode = findPre(head, temp->degree);
            if (insertNode->next == nullptr) {
                insertNode->next = temp;
            } else if (insertNode->next->degree == temp->degree) {
                insertNode->next->coefficient += temp->coefficient;
                free(temp);
            } else if (insertNode->next->degree < temp->degree) {
                temp->next = insertNode->next;
                insertNode->next = temp;
            }
            q = q->next;
        }
        p = p->next;
    }
    return head;
}

void printLinkList(LinkedList L) {
    LNode *p = L->next;
    while (p != nullptr) {
        cout << p->coefficient << "x^" << p->degree << " ";
        p = p->next;
    }
    cout << endl;
}


int main() {
    LinkedList L1 = (LinkedList) malloc(sizeof(LNode));
    LinkedList L2 = (LinkedList) malloc(sizeof(LNode));
    L1->next = nullptr;
    L2->next = nullptr;
    for (int i = 0; i < 3; i++) {
        LinkedList temp1 = (LinkedList) malloc(sizeof(LNode));
        temp1->coefficient = (2 + i);
        temp1->degree = (1 + i);
        temp1->next = L1->next;
        L1->next = temp1;
        LinkedList temp2 = (LinkedList) malloc(sizeof(LNode));
        temp2->coefficient = (4 + i);
        temp2->degree = (i);
        temp2->next = L2->next;
        L2->next = temp2;
    }
    printLinkList(L1);
    printLinkList(L2);
    LinkedList result = calculate(L1, L2);
    printLinkList(result);

    return 0;
}