现在用带头节点的单链表来存储多项式链表中的一个节点表示多项式的一项节点中coef表示多项式的系数exp表示多项式的次数例如5x8用一个节点表示时该节点的coef成员值为5exp值为8。请设计void polySubPolyList LA PolyList LBPolyList LC函数。参数：LALB指向的链表是带头节点的单链表链表中的每个数据节点表示多项式的一项数据节点已经按指数从大到小排序。L

void polySub(PolyList LA, PolyList LB, PolyList LC) { PolyList pa = LA->next; PolyList pb = LB->next; PolyList pc = LC; while (pa != NULL && pb != NULL) { if (pa->exp > pb->exp) { PolyList node = (PolyList)malloc(sizeof(PolyNode)); node->coef = pa->coef; node->exp = pa->exp; pc->next = node; pc = node; pa = pa->next; } else if (pa->exp < pb->exp) { PolyList node = (PolyList)malloc(sizeof(PolyNode)); node->coef = -pb->coef; node->exp = pb->exp; pc->next = node; pc = node; pb = pb->next; } else { int sum = pa->coef - pb->coef; if (sum != 0) { PolyList node = (PolyList)malloc(sizeof(PolyNode)); node->coef = sum; node->exp = pa->exp; pc->next = node; pc = node; } pa = pa->next; pb = pb->next; } } while (pa != NULL) { PolyList node = (PolyList)malloc(sizeof(PolyNode)); node->coef = pa->coef; node->exp = pa->exp; pc->next = node; pc = node; pa = pa->next; } while (pb != NULL) { PolyList node = (PolyList)malloc(sizeof(PolyNode)); node->coef = -pb->coef; node->exp = pb->exp; pc->next = node; pc = node; pb = pb->next; } pc->next = NULL;