基于链表的四位存储大数计算

数据结构的大型实验，和之前写的计算器不同的是，少了词法解析，多了链表指针操作，写完感觉，指针操作能力上了一个台阶，有时间有兴趣的亲，也可以尝试一下，下附实验报告及源码。

1.实验内容

1.1实验目的

实验通过实现基于链表类实现的大数类，从而锻炼对链表的使用和有关大数的四则运算等操作，并在此过程中加深对类的理解和运用。

 

1.2类框架图

1.2.1 Node类

Node类:

1.pre和next都是Node* 类型的指针，分别指向该节点的前驱和后继。

2.num存该节点的数值，大数类实现中采取四位存一个节点的方式，考虑到short的范围，故将数值设置为short类型。

3.Node()是此类的无参构造。

 

1.2.2 myList类

myList类：

 

1.此类有first，tail，mySize三个数据成员，分别代表链表类的的头指针，尾指针和节点数（此链表带一个哨兵，哨兵不计节点数）。

2.myList()和myList(const&myList r)分别为无参构造函数和拷贝构造函数。

3.getSize()返回mySize的值。

4.add_back()和add_front()分别向链表后面和前面插入节点，向前插时，插在哨兵之后。

5.erase()删除尾指针指向的节点，当只剩哨兵时，不做操作。

6.display()因为是逆向存储的，故从后开始输出节点的值，特殊处理，第一个节点需去掉前置0。

7.~myList()析构函数，逐节点移动指针并释放内存。

 

 

 

 

 

1.2.3 BigInt类

BigInt类:

1.BigInt类共3个数据成员，sign，data，digit。sign仅共一次减法运算的符号判断，data即用于存储的myList类。Digit是该大数的位数。

2.该类包含BigInt(),BigInt(strings),BigInt(const &BigInt r)3个构造函数。

3.display(ostream &out)函数用于输出，可以通过改变参数，灵活地进行控制台输出或文件输出。

4.operator系列，其它都没什么特殊，只是因为‘^’操作不宜过大，故将次数值限定在了long long int范围。

5.operator- 因为需要判断正负，故在类的设计上加上了sign，来表示正负。

6.结构图中遗漏了析构函数，~BigInt()通过显示调用data的析构函数进行析构。

 

 

1.3程序流程图

2.实验验证

2.1输入形式

程序开始，需输入指令选择文件输入或键盘输入，其后选择是文件输出，还是屏幕显示。之后，便可输入表达式，表达式的形式需为 a ？ b ，‘？’代表运算符，a，b分别为两大数，两两之间以空格分隔。当全部运算结束，最后输入Ctrl+Z表示结束。

 

2.2输出形式

示例：

输入： 1 + 2

输出： Digit：1  BigInt：3

 

2.3程序功能

可以较快计算大整数的加减乘除模，同时可以较快计算大整数的long long int型幂次方。支持文件/键盘读入，文件输出/屏幕显示。

 

 

 

3.调试分析

3.1技术难点

1.采用四位为一节点逆序存储，虽然能很大程度上加快运算速率，但实现上也颇为复杂。

示例： 123456789   6789->2345->1

2.因为采用的是四位存储模式，需要分别更新大数的位数，和链表的节点数。虽然看似简单，但在实际调试中，因为需要及时更新位数，稍有遗漏就会对大数之间的大小比较产生影响，从而导致整个程序出错。

3.因为不能直接在链表基础上进行四则运算，需要在大数类上对链表进行操作，需通过增加节点，删除节点等操作间接运算，又因体系规模略显庞大，调试过程很容易出错。

4.在函数内生成对象，函数一结束就会被析构，因此需要定义全局变量，或动态生成。

5.因为要提高除法的效率，但又受四位存储的限制，不能直接通过增加节点来使除数有效地逼近被除数，只能先通过增加节点的方式最大限度使除数逼近被除数，然后再用除数乘以一个int型整数的方法逼近被除数，同时将以上过程实现为循环。

 

 

 

 

3.2技术问题及解决方案

Problem1：

乘法效率过低。

Solution1：

采用四位存储模式。

 

Problem2：

除法效率过低。

Solution2：

通过先不断给除数D的拷贝对象A增加0节点，并同时给初始值为1的大整数B增加0节点，再将A乘以一个小整数的方式，找到一个大致接近被除数C的值A，不断循环减去A，并同时在答案上加上B，直至C<A。在外层循环不断重复该过程，直至被除数C小于除数D。

 

Problem3：

求幂效率过低。

Solution3：

类比矩阵多次幂的思想，利用已计算好的较低次幂的乘积直接求得高次幂。具体实现：以十进制为单位，计算一个数的1次，10次，100次，并循环该位上对应的数值次，将答案乘以现乘积……直至与幂的最高位等位。最后乘积即为所求。

 

示例： 2^421

ans=1

//对应个位1

tmp=2^1=2  ans*=tmp

//对应十位2

tmp=2^10=(2^1)^10ans*=tmp ans*=tmp

//对应百位4

tmp=2^100=(2^10)^10ans*=tmp ans*=tmp ans*=tmp ans*=tmp

//最后ans即为所求。

  

Problem4：对象当函数调用完时，会被析构。

Solution4：使用全局变量，或者动态生成变量。

 

3.3调试错误及修正方案

1.写链表类erase()函数时，应把最后一个节点的后继置为NULL，但却因失误多打了一个‘=’，导致链表遍历时，始终无法终止。一直以为是端点处理有问题，最后将‘=’去掉，就顺利通过了。

2.写除法时，始终无法跳出循环，以为是>=重载出了问题，仔细调试后发现是因为>=是基于大数位数判断的，在计算过程中未能及时修正位数，导致>=判断始终成立。随后，在减法操作中不断更新位数，最后顺利跳出循环。

3.局部变量被析构，采取全局变量或者堆区的方法。       

4.测试示例

4.1输入输出示例

1.文件输入，文件输出

 

 

 

2.文件输入，屏幕输出

 

 

3.控制台输入，屏幕输出

 

 

 

4.控制台输入，文件输出

 

 

4.2加法示例

4.3减法示例

 

 

4.4乘法示例

 

 

 

 

 

大数据测试时因控制台输入有限且不便，故采用文件流测试。此处可大致认为是两个10000位的数相乘，耗时4.6s。

 

4.5除法示例

4.6求幂示例

大数据测试（需考虑文件流输出稍慢）：

 

4.7取模示例

4.源码及注释

//myList.h声明#ifndef  MYLIST#define MYLIST#include <iostream>using namespace std;//Node类class Node{public:short num; //每四位存一节点Node* pre;//指向该节点前驱Node* next; //指向该节点后继Node()//无参构造{num = 0;next = NULL;pre = NULL;}};typedef  Node*  NodePointer;class myList{public:myList();myList(const myList& rightHandSide);//拷贝构造~myList();int   getSize() const;void add_back(int val);void add_front(int val);void display(ostream &out)const;//输出列表元素（遍历）void erase();myList  &operator =(const myList&  rightHandSide);NodePointer tail;  //表尾指针NodePointer first; //表首指针private:int mySize;};#endif // ! MYLIST

#include "myList.h"#include <string>myList::myList(){first = new Node(); //默认一个哨兵节点tail = first;mySize = 0;}myList::myList(const myList& rightHandSide){    first = new Node();NodePointer tmp1=first;NodePointer tmp2=rightHandSide.first;NodePointer tmp3;mySize = rightHandSide.mySize;tmp2 = tmp2->next; //遍历rightHandSide逐节点拷贝while (tmp2 != NULL) {tmp3 = new Node();tmp3->num = tmp2->num;tmp1->next = tmp3;tmp3->pre = tmp1;tmp1 = tmp3;tmp2 = tmp2->next;}tail = tmp1;}void myList::add_back(int val)//插入到链表尾部{Node *newNode = new Node();newNode->num = val;newNode->pre = tail;(*tail).next = newNode;tail = newNode;mySize++;}void myList::add_front(int val)//插入在哨兵之后，现第一个节点之前{Node *newNode = new Node();newNode->num = val;newNode->pre = first;if (first->next)(*first->next).pre = newNode;else tail = newNode;newNode->next = first->next;first->next = newNode;mySize++;}int myList::getSize() const{return mySize;}void myList::display(ostream &out)const //遍历输出{Node* tmp = tail;if (tmp != first)out << tmp->num;else return;tmp = tmp->pre;while (tmp != first){int i = 0, temp = tmp->num;if (temp == 0)i = 1;//特殊情况处理，0视为1位while (temp){temp /= 10;i++;}out << string(4 - i, '0'); //如果不是最后一个节点，输出时补0。out << tmp->num;tmp = tmp->pre;}}myList::~myList()//遍历析构{Node *tmp;while (first){tmp = first;first = first->next;delete tmp;}}void myList::erase()//删除最后一个节点{if (mySize>0){NodePointer tmp;tmp = tail;tail = tmp->pre;        delete tmp;tail->next = NULL;//就是此处调试了许久mySize--;}}myList & myList::  operator=(const myList&  rightHandSide){if (this == &rightHandSide)return *this;//排除自拷贝else{NodePointer tmp1 = first;NodePointer tmp2 = rightHandSide.first;NodePointer tmp3;//比较大小，采取不同拷贝模式if (mySize >= rightHandSide.mySize){//先拷贝现有节点，再删除多余节点while (tmp2 != NULL){tmp1->num = tmp2->num;if (tmp2->next == NULL)break;tmp2 = tmp2->next;tmp1 = tmp1->next;}tail = tmp1;tmp1 = tmp1->next;while (tmp1 != NULL){tmp3 = tmp1;tmp1 = tmp1->next;delete tmp3;}tail->next = NULL;}else{//先拷贝现有节点，再添加多余节点while (1){tmp1->num = tmp2->num;if (tmp1->next == NULL)break;tmp2 = tmp2->next;tmp1 = tmp1->next;}while (1){tmp2 = tmp2->next;if (tmp2 == NULL)break;tmp3 = new Node;tmp3->pre = tmp1;tmp3->num = tmp2->num;tmp1->next = tmp3;tmp1 = tmp3;}tail = tmp1;}mySize = rightHandSide.mySize;return *this;}}

//BigInt.h#ifndef BIGINT#define BIGINT#include<string>#include"myList.h"class BigInt{private:myList data;int digit;//大数位数bool sign;//只做为减法做一次判断public://构造函数BigInt();BigInt(string s);BigInt(const BigInt & x);//显示函数void display(ostream &out);//各类运算符重载BigInt &operator =(const BigInt &x);BigInt  &operator +(const BigInt &x);BigInt  &operator -(const BigInt &x);bool operator >(const BigInt &x);bool operator >=(const BigInt &x);BigInt  &operator *(const BigInt &x);BigInt  &operator /(const BigInt &x);BigInt  &operator %(const BigInt &x);BigInt  &operator *(const int &x);BigInt  &operator ^(const long long int &x);//析构函数~BigInt();//更新位数void modifyDigit(BigInt &x);};#endif // !BIGINT

//BigInt.cpp#include <algorithm>#include <string>#include"BigInt.h"BigInt *replace1 = new BigInt();//全局变量BigInt *replace2 = new BigInt();BigInt *empty = new BigInt();//空节点BigInt zero(string(1, '0'));//大数值为0，供函数使用BigInt one(string(1, '1'));//大数值为1，供函数使用//构造函数BigInt::BigInt(){myList();sign = false;digit = 0;}BigInt::BigInt(string s){myList();sign = false;digit = s.length();reverse(s.begin(), s.end());/*每四位存一个节点，逆向存储，最前面不够的补0，方便统一转换*/int n = s.length() % 4;if (n != 0)s += string(4 - n, '0');int t = s.length() / 4;int tmp = 0;for (int i = 0; i < t; i++){tmp = 0;tmp += s[i * 4] - '0';tmp += (s[i * 4 + 1] - '0') * 10;tmp += (s[i * 4 + 2] - '0') * 100;tmp += (s[i * 4 + 3] - '0') * 1000;data.add_back(tmp);}}BigInt::BigInt(const BigInt & x){sign = x.sign;data = x.data;digit = x.digit;}//操作符重载BigInt & BigInt::operator =(const BigInt &x){sign = x.sign;data = x.data;digit = x.digit;return *this;}bool BigInt::operator >(const BigInt &x){if (digit > x.digit)return true;//位数判断，因此计算过程中需不断修正else if (digit < x.digit)return false;else{NodePointer p1 = data.tail, p2 = x.data.tail;while (p1 != NULL){if (p1->num > p2->num)return true;else if (p1->num < p2->num)return false;else{p1 = p1->pre;p2 = p2->pre;}}return false;//到这里说明相等}}bool BigInt::operator >=(const BigInt &x){if (digit > x.digit)return true;else if (digit < x.digit)return false;else{NodePointer p1 = data.tail, p2 = x.data.tail;while (p1 != NULL){if (p1->num > p2->num)return true;else if (p1->num < p2->num)return false;else{p1 = p1->pre;p2 = p2->pre;}}return true;//到这里说明相等}}BigInt& BigInt:: operator +(const BigInt &x){*replace1 = *this;*replace2 = x;int t = data.getSize() - replace2->data.getSize();//将节点数补成相同if (t >= 0){while (t){replace2->data.add_back(0);t--;}}else{while (t){replace1->data.add_back(0);t++;}}int flag = 0, tmp;NodePointer p1, p2;p1 = replace1->data.first;p2 = replace2->data.first;//删除前置0节点while (1){if (p1->next == NULL)break;tmp = p1->num + p2->num + flag;p1->num = tmp % 10000;flag = tmp / 10000;p1 = p1->next;p2 = p2->next;}tmp = p1->num + p2->num+ flag;p1->num = tmp % 10000;if (tmp >= 10000)replace1->data.add_back(1); //修正位数replace1->digit = (replace1->data.getSize() - 1) * 4;int lastNode = replace1->data.tail->num;if (lastNode < 10)replace1->digit += 1;else if (lastNode >= 10 && lastNode<100)replace1->digit += 2;else if (lastNode >= 100 && lastNode<1000)replace1->digit += 3;else replace1->digit += 4;return *replace1;}BigInt& BigInt:: operator -(const BigInt &x){*replace1 = *this;*replace2 = x;int t = replace1->data.getSize() - replace2->data.getSize();NodePointer p1, p2;//p1是大的那个数,p2是小的那个数bool symbol = false;//函数返回值是replace1还是replace2的标记if (*replace2 > *replace1){replace2->sign = true;p1 = replace2->data.first;p2 = replace1->data.first;}else{symbol = true;p1 = replace1->data.first;p2 = replace2->data.first;}if (t >= 0){while (t--){replace2->data.add_back(0);}}else{while (t++){replace1->data.add_back(0);}}int flag = 0, tmp;while (p1 != NULL){tmp = p1->num - p2->num + flag;if (tmp < 0){tmp += 10000;flag = -1;}else flag = 0;p1->num = tmp;p1 = p1->next;p2 = p2->next;}if (symbol){p1 = replace1->data.tail;while (1){if (p1->num != 0 || p1->pre == replace1->data.first)break;p1 = p1->pre;replace1->data.erase();}replace1->digit = (replace1->data.getSize() - 1) * 4;int lastNode = (*(replace1->data.tail)).num;if (lastNode < 10)replace1->digit += 1;else if (lastNode >= 10 && lastNode<100)replace1->digit += 2;else if (lastNode >= 100 && lastNode<1000)replace1->digit += 3;else replace1->digit += 4;return *replace1;}else{p1 = replace2->data.tail;while (1){if (p1->num != 0 || p1->pre == replace2->data.first)break;p1 = p1->pre;replace2->data.erase();}replace2->digit = (replace2->data.getSize() - 1) * 4;int lastNode = (*(replace2->data.tail)).num;if (lastNode < 10)replace2->digit += 1;else if (lastNode >= 10 && lastNode<100)replace2->digit += 2;else if (lastNode >= 100 && lastNode<1000)replace2->digit += 3;else replace2->digit += 4;return *replace2;}}BigInt& BigInt:: operator *(const BigInt &x){//特判if (x.digit==1&&x.data.tail->num == 0){BigInt *ans = new BigInt(zero);return *ans;}else if (x.digit == 1 && x.data.tail->num == 1){BigInt *ans = new BigInt(*this);return *ans;}else{*replace1 = *empty;*replace2 = *empty;NodePointer p1, p2;p1 = this->data.first;int count = 0;while (1){*replace2 = *empty;//乘法中的挪位for (int i = 0; i < count; i++){replace2->data.add_back(0);}p1 = p1->next;if (p1 == NULL)break;p2 = x.data.first;int flag = 0, tmp1;while (1){p2 = p2->next;if (p2 == NULL)break;tmp1 = p1->num * p2->num + flag;flag = tmp1 / 10000;tmp1 %= 10000;(*replace2).data.add_back(tmp1);}if(flag)/*此处有依据，9999*9999=99980001，就算再怎么进位，也只会多出一个节点*/{(*replace2).data.add_back(flag);}*replace1 = *replace1 + *replace2;count++;}return *replace1;}}BigInt& BigInt:: operator *(const int &x){*replace1 = *this;NodePointer p1;p1 = replace1->data.first;int flag = 0,tmp;while (1){p1 = p1->next;if (p1 == NULL)break;tmp = (p1->num)*x + flag;flag = tmp / 10000;p1->num =(tmp)% 10000;}while (flag){replace1->data.add_back(flag%10000);flag /= 10000;}replace1->digit = (replace1->data.getSize() - 1) * 4;tmp = (*(replace1->data.tail)).num;//修正位数if (tmp < 10)replace1->digit += 1;else if (tmp >= 10 && tmp<100)replace1->digit += 2;else if (tmp >= 100 && tmp<1000)replace1->digit += 3;else replace1->digit += 4;return *replace1;}BigInt& BigInt:: operator /(const BigInt &x){BigInt *divisor=new BigInt(x);BigInt *dividend = new BigInt(*this);//特判if (divisor->digit == 1 && divisor->data.tail->num == 1){return *dividend;}else if (*divisor> *dividend){BigInt *ans = new BigInt(zero);return *ans;}else {BigInt *ans = new BigInt(*empty);ans->data.add_back(0);while ((*dividend)>=(*divisor)){BigInt tmp1(*divisor),tmp2(one);int count = dividend->digit - divisor->digit;count = (count - 1) / 4;//补节点0for (int i = 0; i < count; i++){tmp1.data.add_front(0);tmp1.digit += 4;tmp2.data.add_front(0);tmp2.digit += 4;}int multi = 1;int t = (dividend->digit) - (tmp1.digit)-1;for (int i = 0; i < t; i++){multi *= 10;}//继续逼近tmp1 = tmp1*multi;tmp2 = tmp2*multi;while ((*dividend)>=tmp1){*ans = (*ans) + tmp2;*dividend = (*dividend) - tmp1;}}return *ans;}}BigInt& BigInt:: operator ^(const long long int &x){BigInt *tmp1 = new BigInt();BigInt *tmp2 = new BigInt();*tmp1 = *this;*tmp2 = *empty;tmp2->data.add_back(1);long long int store = x;int tmp;while (store){tmp = store % 10;for (int i = 0; i < tmp; i++){*tmp2 = (*tmp2)*(*tmp1);}*tmp1 = (*tmp1)*(*tmp1);BigInt temp(*tmp1);*tmp1 = (*tmp1)*(*tmp1);*tmp1 = (*tmp1)*(*tmp1);*tmp1 = *tmp1 * temp;store /= 10;}return *tmp2;}BigInt& BigInt:: operator %(const BigInt &x){BigInt *divisor = new BigInt(x);BigInt *dividend = new BigInt(*this);//特判if (divisor->digit == 1 && divisor->data.tail->num == 1){BigInt *ans = new BigInt(zero);return *ans;}else if (*divisor> *dividend){return *dividend;}else{while ((*dividend) >= (*divisor)){BigInt tmp1(*divisor);int count = dividend->digit - divisor->digit;count = (count - 1) / 4;//补节点0for (int i = 0; i < count; i++){tmp1.data.add_front(0);tmp1.digit += 4;}int multi = 1;int t = (dividend->digit) - (tmp1.digit) - 1;for (int i = 0; i < t; i++){multi *= 10;}//再继续逼近tmp1 = tmp1*multi;while ((*dividend) >= tmp1){*dividend = (*dividend) - tmp1;}}return *dividend;}}void BigInt::display(ostream &out){out << "Digit is: " << digit;out << "   BigInt is: ";//sign正负标记if (sign)out << '-';data.display(out);}//位数修正void BigInt::modifyDigit(BigInt &x){x.digit = (x.data.getSize() - 1) * 4;int lastNode = (*(x.data.tail)).num;if (lastNode < 10)x.digit += 1;else if (lastNode >= 10 && lastNode<100)x.digit += 2;else if (lastNode >= 100 && lastNode<1000)x.digit += 3;else x.digit += 4;}BigInt::~BigInt(){data.~myList();}

//main.cpp#include "BigInt.h"#include<iostream>#include "stdio.h"#include <time.h>#include <fstream>#include "windows.h"//输入显示void input_display(){cout << "If you want to choose FileInput,please enter F/f.\n";cout << "If you want to choose ConsoleInput,please enter C/c.\n";}//输出显示void out_display(){cout << "If you want to choose FileOutput,please enter F/f.\n";cout << "If you want to choose ScreenOutput,please enter S/s.\n";}//string转long long intlong long int stringToInt(string s){long long int ans = 0,multi=1;for (int i = s.length() - 1; i >= 0; i--){ans += multi*(s[i] - '0');multi *= 10;}return ans;}int main(){char command;string s1, s2;long long int c;char oper;clock_t start, end;string zero0 = "0";while (1){input_display();cin >> command;//判断是控制台输入还是文件输入if (command == 'C' || command == 'c'){system("cls");out_display();cin >> command;system("cls");//判断是屏幕输出还是文件输出if (command == 'S' || command == 's'){while (cin >> s1 >> oper >> s2){if (oper != '^')//区别^和其他运算符{BigInt a(s1), b(s2);start = clock();if (oper == '+')     b = a + b;else if (oper == '-')b = a - b;else if (oper == '*')b = a * b;else if (oper == '/'){if (s2 == zero0){cout << "Error:  Divided by 0\n\n";continue;}else b = a / b;}else if (oper == '%')b = a % b;else{cout << "Invalid operator.\nOnly display the value of a and b:\na:  ";a.display(cout);cout << endl<<"b:  ";}end = clock();b.display(cout);cout << endl;cout << "Calculation takes " << end - start << "ms\n\n";}else{c = stringToInt(s2);BigInt a(s1);start = clock();a = a^c;end = clock();a.display(cout);cout << endl;cout << "Calculation takes " << end - start << "ms\n\n";}}}else{string s1, s2,filename;long long int c;char oper;clock_t start, end;cout << "Please enter the name for the storage file!\n";cin >> filename;filename += ".txt";//已处理后缀名ofstream fout(filename,ios::app);//输出文件流system("cls");while (cin >> s1 >> oper >> s2){if (oper != '^'){BigInt a(s1), b(s2);start = clock();if (oper == '+')     b = a + b;else if (oper == '-')b = a - b;else if (oper == '*')b = a * b;else if (oper == '/'){if (s2 == zero0){fout << "Error:  Divided by 0\n\n";continue;}b = a / b;}else if (oper == '%')b = a % b;else{fout << "Invalid operator.\nOnly display the value of a and b:\na:  ";a.display(fout);fout << endl << "b:  ";}end = clock();b.display(fout);fout << endl;fout << "Calculation takes " << end - start << "ms\n\n";fout.flush();}else{c = stringToInt(s2);BigInt a(s1);start = clock();a = a^c;end = clock();a.display(fout);fout << endl;fout << "Calculation takes " << end - start << "ms\n\n";fout.flush();}}fout.close();}break;}else if (command == 'F' || command == 'f'){system("cls");out_display();cin >> command;if (command == 'F' || command == 'f'){system("cls");string filein, fileout;cout << "Please enter the calculate filename\n";cin >> filein;cout << "\nPlease enter the storage filename\n";cin >> fileout;filein += ".txt";fileout += ".txt";ifstream fin(filein);ofstream fout(fileout);while (fin >> s1 >> oper >> s2){if (oper != '^'){BigInt a(s1), b(s2);start = clock();if (oper == '+')     b = a + b;else if (oper == '-')b = a - b;else if (oper == '*')b = a * b;else if (oper == '/'){if (s2 == zero0){fout << "Error:  Divided by 0\n\n";continue;}b = a / b;}else if (oper == '%')b = a % b;else{fout << "Invalid operator.\nOnly display the value of a and b:\na:  ";a.display(fout);fout << endl << "b:  ";}end = clock();b.display(fout);fout << endl;fout << "Calculation takes " << end - start << "ms\n\n";fout.flush();}else{system("cls");c = stringToInt(s2);BigInt a(s1);start = clock();a = a^c;end = clock();a.display(fout);fout << endl;fout << "Calculation takes " << end - start << "ms\n\n";fout.flush();}}fout.close();break;}else{string filein;cout << "Please enter the calculate filename\n";cin >> filein;filein += ".txt";ifstream fin(filein);while (fin >> s1 >> oper >> s2){if (oper != '^'){BigInt a(s1), b(s2);start = clock();if (oper == '+')     b = a + b;else if (oper == '-')b = a - b;else if (oper == '*')b = a * b;else if (oper == '/'){if (s2 == zero0){cout << "Error:  Divided by 0\n\n";continue;}b = a / b;}else if (oper == '%')b = a % b;else{cout << "Invalid operator.\nOnly display the value of a and b:\na:  ";a.display(cout);cout << endl << "b:  ";}end = clock();b.display(cout);cout << endl;cout << "Calculation takes " << end - start << "ms\n\n";}else{c = stringToInt(s2);BigInt a(s1);start = clock();a = a^c;end = clock();a.display(cout);cout << endl;cout << "Calculation takes " << end - start << "ms\n\n";}}break;}}else if (command == 'E' || command == 'e')//e退出{exit(0);}else{system("cls");cout << "Invalid Input!!!\n";}}system("pause");}