HDU 4927 大数运算

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std; 

#define MAXN 9999
#define MAXSIZE 10
#define DLEN 4

class BigInt
{ 
private: 
    int a[500];    //可以控制大数的位数 
    int len;       //大数长度
public: 
    BigInt(){ len = 1;memset(a,0,sizeof(a)); }   //构造函数
    BigInt(const int);       //将一个int类型的变量转化为大数
    BigInt(const char*);     //将一个字符串类型的变量转化为大数
    BigInt(const BigInt &);  //拷贝构造函数
    BigInt &operator=(const BigInt &);   //重载赋值运算符，大数之间进行赋值运算

    friend istream& operator>>(istream&,  BigInt&);   //重载输入运算符
    friend ostream& operator<<(ostream&,  BigInt&);   //重载输出运算符

    BigInt operator+(const BigInt &) const;   //重载加法运算符，两个大数之间的相加运算 
    BigInt operator-(const BigInt &) const;   //重载减法运算符，两个大数之间的相减运算 
    BigInt operator*(const BigInt &) const;   //重载乘法运算符，两个大数之间的相乘运算 
    BigInt operator/(const int   &) const;    //重载除法运算符，大数对一个整数进行相除运算

    BigInt operator^(const int  &) const;    //大数的n次方运算
    int    operator%(const int  &) const;    //大数对一个int类型的变量进行取模运算    
    bool   operator>(const BigInt & T)const;   //大数和另一个大数的大小比较
    bool   operator<(const BigInt & T) const;
    bool   operator==(const BigInt & T) const;
    bool   operator>(const int & t)const;      //大数和一个int类型的变量的大小比较
    bool   operator<(const int &t) const;
    bool   operator==(const int &t) const; 

    void print();       //输出大数
}; 

bool BigInt::operator==(const BigInt & T) const {
    return !(*this > T) && !(T > *this);
}
bool BigInt::operator==(const int &t) const {
    BigInt T = BigInt(t);
    return *this == T;
}
bool BigInt::operator<(const BigInt & T) const {
    return T > *this;    
}
bool BigInt::operator<(const int &t) const {
    return BigInt(t) > *this;
}
BigInt::BigInt(const int b)     //将一个int类型的变量转化为大数
{ 
    int c,d = b;
    len = 0;
    memset(a,0,sizeof(a));
    while(d > MAXN)
    {
        c = d - (d / (MAXN + 1)) * (MAXN + 1); 
        d = d / (MAXN + 1);
        a[len++] = c;
    }
    a[len++] = d;
}
BigInt::BigInt(const char*s)     //将一个字符串类型的变量转化为大数
{
    int t,k,index,l,i;
    memset(a,0,sizeof(a));
    l=strlen(s);   
    len=l/DLEN;
    if(l%DLEN)
        len++;
    index=0;
    for(i=l-1;i>=0;i-=DLEN)
    {
        t=0;
        k=i-DLEN+1;
        if(k<0)
            k=0;
        for(int j=k;j<=i;j++)
            t=t*10+s[j]-‘0‘;
        a[index++]=t;
    }
}
BigInt::BigInt(const BigInt & T) : len(T.len)  //拷贝构造函数
{ 
    int i; 
    memset(a,0,sizeof(a)); 
    for(i = 0 ; i < len ; i++)
        a[i] = T.a[i]; 
} 
BigInt & BigInt::operator=(const BigInt & n)   //重载赋值运算符，大数之间进行赋值运算
{
    int i;
    len = n.len;
    memset(a,0,sizeof(a)); 
    for(i = 0 ; i < len ; i++) 
        a[i] = n.a[i]; 
    return *this; 
}
istream& operator>>(istream & in,  BigInt & b)   //重载输入运算符
{
    char ch[MAXSIZE*4];
    int i = -1;
    in>>ch;
    int l=strlen(ch);
    int count=0,sum=0;
    for(i=l-1;i>=0;)
    {
        sum = 0;
        int t=1;
        for(int j=0;j<4&&i>=0;j++,i--,t*=10)
        {
            sum+=(ch[i]-‘0‘)*t;
        }
        b.a[count]=sum;
        count++;
    }
    b.len =count++;
    return in;

}
ostream& operator<<(ostream& out,  BigInt& b)   //重载输出运算符
{
    int i;  
    cout << b.a[b.len - 1]; 
    for(i = b.len - 2 ; i >= 0 ; i--)
    { 
        cout.width(DLEN); 
        cout.fill(‘0‘); 
        cout << b.a[i]; 
    } 
    return out;
}

BigInt BigInt::operator+(const BigInt & T) const   //两个大数之间的相加运算
{
    BigInt t(*this);
    int i,big;      //位数   
    big = T.len > len ? T.len : len; 
    for(i = 0 ; i < big ; i++) 
    { 
        t.a[i] +=T.a[i]; 
        if(t.a[i] > MAXN) 
        { 
            t.a[i + 1]++; 
            t.a[i] -=MAXN+1; 
        } 
    } 
    if(t.a[big] != 0)
        t.len = big + 1; 
    else
        t.len = big;   
    return t;
}
BigInt BigInt::operator-(const BigInt & T) const   //两个大数之间的相减运算 
{  
    int i,j,big;
    bool flag;
    BigInt t1,t2;
    if(*this>T)
    {
        t1=*this;
        t2=T;
        flag=0;
    }
    else
    {
        t1=T;
        t2=*this;
        flag=1;
    }
    big=t1.len;
    for(i = 0 ; i < big ; i++)
    {
        if(t1.a[i] < t2.a[i])
        { 
            j = i + 1; 
            while(t1.a[j] == 0)
                j++; 
            t1.a[j--]--; 
            while(j > i)
                t1.a[j--] += MAXN;
            t1.a[i] += MAXN + 1 - t2.a[i]; 
        } 
        else
            t1.a[i] -= t2.a[i];
    }
    t1.len = big;
    while(t1.a[t1.len - 1] == 0 && t1.len > 1)
    {
        t1.len--;
        big--;
    }
    if(flag)
        t1.a[big-1]=0-t1.a[big-1];
    return t1; 
} 

BigInt BigInt::operator*(const BigInt & T) const   //两个大数之间的相乘运算 
{ 
    BigInt ret; 
    int i,j,up; 
    int temp,temp1;   
    for(i = 0 ; i < len ; i++)
    { 
        up = 0; 
        for(j = 0 ; j < T.len ; j++)
        { 
            temp = a[i] * T.a[j] + ret.a[i + j] + up; 
            if(temp > MAXN)
            { 
                temp1 = temp - temp / (MAXN + 1) * (MAXN + 1); 
                up = temp / (MAXN + 1); 
                ret.a[i + j] = temp1; 
            } 
            else
            { 
                up = 0; 
                ret.a[i + j] = temp; 
            } 
        } 
        if(up != 0) 
            ret.a[i + j] = up; 
    } 
    ret.len = i + j; 
    while(ret.a[ret.len - 1] == 0 && ret.len > 1)
        ret.len--; 
    return ret; 
} 
BigInt BigInt::operator/(const int & b) const   //大数对一个整数进行相除运算
{ 
    BigInt ret; 
    int i,down = 0;   
    for(i = len - 1 ; i >= 0 ; i--)
    { 
        ret.a[i] = (a[i] + down * (MAXN + 1)) / b;
        down = a[i] + down * (MAXN + 1) - ret.a[i] * b;
    } 
    ret.len = len; 
    while(ret.a[ret.len - 1] == 0 && ret.len > 1)
        ret.len--; 
    return ret; 
}
int BigInt::operator %(const int & b) const    //大数对一个int类型的变量进行取模运算    
{
    int i,d=0;
    for (i = len-1; i>=0; i--)
    {
        d = ((d * (MAXN+1))% b + a[i])% b;  
    }
    return d;
}
BigInt BigInt::operator^(const int & n) const    //大数的n次方运算
{
    BigInt t,ret(1);
    int i;
    if(n<0)
        exit(-1);
    if(n==0)
        return 1;
    if(n==1)
        return *this;
    int m=n;
    while(m>1)
    {
        t=*this;
        for( i=1;i<<1<=m;i<<=1)
        {
            t=t*t;
        }
        m-=i;
        ret=ret*t;
        if(m==1)
            ret=ret*(*this);
    }
    return ret;
}
bool BigInt::operator>(const BigInt & T) const   //大数和另一个大数的大小比较
{ 
    int ln; 
    if(len > T.len)
        return true; 
    else if(len == T.len)
    { 
        ln = len - 1; 
        while(a[ln] == T.a[ln] && ln >= 0)
            ln--; 
        if(ln >= 0 && a[ln] > T.a[ln])
            return true; 
        else
            return false; 
    } 
    else
        return false; 
}
bool BigInt::operator >(const int & t) const    //大数和一个int类型的变量的大小比较
{
    BigInt b(t);
    return *this>b;
}

void BigInt::print()    //输出大数
{ 
    int i;  
    printf("%d", a[len-1]);
    for (int i = len-2; i >= 0; --i) {
        printf("%04d", a[i]);
    }
    puts("");
}
int main()
{
    //freopen("1007.in","r",stdin);
    int tt,n,a[3005];
    scanf("%d",&tt);
    while(tt--)
    {
        scanf("%d",&n);
        BigInt Z(1),ans(0),tmp;
        bool zheng=1;
        for(int i=1; i<=n; i++)
            scanf("%d",&a[i]);
        for(int i=0; i<=n-1; i++)
        {
            if(i>0) Z=(Z*(BigInt)(n-i))/i;
            if(i%2==0)
            {
                tmp=Z*(BigInt)(a[n-i]);
                if(zheng)
                    ans=ans+tmp;
                else
                {
                    if(ans<tmp)
                    {
                        ans=tmp-ans;
                        zheng=1;
                    }
                    else
                        ans=ans-tmp;
                }
            }
            else
            {
                tmp=(Z*(BigInt)(a[n-i]));
                if(zheng)
                {
                    if(ans<tmp)
                    {
                        ans=tmp-ans;
                        zheng=0;
                    }
                    else
                        ans=ans-tmp;
                }else
                    ans=ans+tmp;
            }
        }
        if(!zheng) cout<<‘-‘;
        ans.print();
    }
    return 0;
}