怎么通过浙大数据结构《一元多项式的乘法和加法》的第四个测试用例

Question

这是题目信息：
02-线性结构2 一元多项式的乘法与加法运算 （20 point(s)）

下面是我的代码：

 #include<iostream>
using namespace std;
typedef struct PolyNode *PolyPtr;
struct PolyNode{
    int coef;
    int expo;
    PolyPtr next;
};

PolyPtr readPoly();
PolyPtr Add(PolyPtr A, PolyPtr B);
PolyPtr Mult(PolyPtr A, PolyPtr B);
void Attach(int c,int e,PolyPtr *LPtr);
void PrintPoly(PolyPtr LPtr);

int main(int argc, char const *argv[])
{
    PolyPtr A,B,A1,B1;
    A = readPoly();
    B = readPoly();
    B1 = Mult(A,B);
    PrintPoly(B1);
    A1 = Add(A,B);
    PrintPoly(A1);

    return 0;
}

PolyPtr readPoly()
{
    int N,c,e;
    PolyPtr LPtr,head;
    head = new PolyNode;
    head->next = NULL;
    LPtr = head;
    scanf("%d",&N);
    while(N--)
    {
        scanf("%d%d",&c,&e);
        Attach(c,e,&LPtr);
    }
    return head;//返回头节点
}

void Attach(int c,int e, PolyPtr *LPtr)
{
    PolyPtr temp;
    temp = new PolyNode;
    temp->next = NULL;

    temp->coef = c;
    temp->expo = e;
    (*LPtr)->next = temp;
    *LPtr = temp;
}

PolyPtr Add(PolyPtr A, PolyPtr B)
{
    PolyPtr head,LPtr;
    int sum;
    head = new PolyNode;
    head->next = NULL;
    LPtr = head;
    A = A->next;
    B = B->next;
    while(A&&B)
    {
        if(A->expo == B->expo)//如果两项的指数相同
        {
            sum = A->coef + B->coef;
            if(sum)
                Attach(sum, A->expo, &LPtr);
            A = A->next;
            B = B->next;
        }

        else if(A->expo > B->expo)
        {
            if(A->coef)
                 Attach(A->coef,A->expo,&LPtr);
            A = A->next;
        }
        else{
            if(B->coef)
               Attach(B->coef,B->expo,&LPtr);
            B = B->next;
        }
    }
    for(;A;A = A->next)Attach(A->coef,A->expo,&LPtr);
    for(;B;B = B->next)Attach(B->coef, B->expo,&LPtr);

    return head;
}

PolyPtr Mult(PolyPtr A, PolyPtr B)
{
    int c,e;
    A = A->next;
    B = B->next;
    if(!A||!B)return NULL;

    PolyPtr temp,B0,head,LPtr;
    head = new PolyNode;
    head->next = NULL;
    LPtr = head;
    B0 = B;

    while(B)//先用A的第一项乘B，得到一个结果表达式
    {
        Attach(A->coef*B->coef, A->expo+B->expo, &LPtr);
        B = B->next;
    }
    A = A->next;
    while(A)
    {
        B = B0;
        LPtr = head;
        while(B)
        {
            c = A->coef * B->coef;
            e = A->expo + B->expo;
            while(LPtr->next && LPtr->next->expo > e)
                LPtr = LPtr->next;
            if(LPtr->next && LPtr->next->expo == e)
            {
                if(LPtr->next->coef + c)
                    LPtr->next->coef += c;
                else{
                    temp = LPtr->next;
                    LPtr->next = temp->next;
                    delete temp;
                }
            }
            else{
                temp = new PolyNode;
                temp->coef = c;
                temp->expo = e;
                temp->next = LPtr->next;
                LPtr->next = temp;
                LPtr = LPtr->next;
            }
            B = B->next;
        }
        A = A->next;
    }
    return head;
}

void PrintPoly(PolyPtr LPtr)
{
    LPtr = LPtr->next;
    int flag = 1;
    if(!LPtr){
        printf("0 0\n");
        return;
    }
    while(LPtr)
    {
        if(flag == 1)flag = 0;
        else{
            printf(" ");
        }
        printf("%d %d",LPtr->coef,LPtr->expo);
        LPtr = LPtr->next;
    }
    printf("\n");
}

不知道哪里有问题，一直不能通过第四个用例，请大神帮忙看一下，谢谢！