用代码写出实现两多项式相加的完整算法假定储存两多项式的带头节点的单链表HaHb已经建立好

void addPoly(PolyNode *Ha, PolyNode *Hb) {
    PolyNode *pa = Ha->next, *pb = Hb->next, *pc = Ha;
    while (pa && pb) {
        if (pa->expn < pb->expn) {
            pc->next = pa;
            pc = pa;
            pa = pa->next;
        } else if (pa->expn > pb->expn) {
            pc->next = pb;
            pc = pb;
            pb = pb->next;
        } else {
            float sum = pa->coef + pb->coef;
            if (fabs(sum) > 1e-5) {
                pa->coef = sum;
                pc->next = pa;
                pc = pa;
                pa = pa->next;
                PolyNode *tmp = pb;
                pb = pb->next;
                free(tmp);
            } else {
                PolyNode *tmp = pa;
                pa = pa->next;
                free(tmp);
                tmp = pb;
                pb = pb->next;
                free(tmp);
            }
        }
    }
    if (pa) {
        pc->next = pa;
    } else {
        pc->next = pb;
    }
    free(Hb);
}