bigInt.cpp

#include<iostream>
#include<string>
#include<time.h>
#include "bigInt.h"
using namespace std;

BigInt::BigInt(){	//构造函数
	head = tail = temp = NULL;
	symbol = '+';
	length = 0;
}

BigInt::BigInt(const BigInt &bigNum){	//复制构造函数
	NumUnit *p;

	head = tail = temp = NULL;
	symbol = bigNum.symbol;
	length = 0;
	p = bigNum.tail;
	while (p){
		insertHead(p->num);
		p = p->prev;
	}
}

BigInt::~BigInt(){	//析构函数
	if (head == NULL) return;
	NumUnit *next;

	temp = head;
	while (temp){
		next = temp->next;
		delete temp;
		temp = next;
	}
	head = tail = temp = NULL;
}

void BigInt::randBigNum(){	//随机产生数
	int MAX = rand() % 49;

	for (int i = 1; i < MAX; i++){
		insertHead(rand() % 10);
	}
	insertHead(rand() % 9 + 1);
}

void BigInt::insertHead(int num){	//插入到头部
	temp = new NumUnit;
	temp->num = num;
	temp->prev = NULL;
	if (!head){
		head = tail = temp;
		temp->next = NULL;
	}
	else{
		temp->next = head;
		head->prev = temp;
		head = temp;
	}
	length++;
}

void BigInt::deleteHead(){	//头部为0时删除头部
	temp = head;
	head = head->next;
	delete temp;
	length--;
	if (length == 0) symbol = '+';	//长度为0时，符号为+
}

BigInt BigInt::operator + (const BigInt &bigNum) const{	// + 的重载
	BigInt result;
	NumUnit *num1 = tail, *num2 = bigNum.tail;
	int sum, carry = 0;
	
	if (symbol != bigNum.symbol){
		result = *this - bigNum;
		return result;
	}
	result.symbol = symbol;
	while (num1 && num2){
		sum = num1->num + num2->num + carry;
		carry = sum / 10;
		sum %= 10;
		result.insertHead(sum);
		num1 = num1->prev;
		num2 = num2->prev;
	}
	if (num2)num1 = num2;
	while (num1){
		sum = num1->num + carry;
		carry = sum / 10;
		sum %= 10;
		result.insertHead(sum);
		num1 = num1->prev;
	}
	if (carry)
		result.insertHead(carry);
	return result;
}

BigInt BigInt::operator - (const BigInt &bigNum) const{	// - 的重载
	BigInt result;
	NumUnit *num1 = tail, *num2 = bigNum.tail;
	int sub, carry = 0;

	if (symbol != bigNum.symbol){
		result = *this + -bigNum;
		return result;
	}
	if (*this < bigNum){
		result = -(bigNum - *this);
		return result;
	}
	result.symbol = symbol;
	while (num1 && num2){
		sub = num1->num - num2->num - carry;
		sub += 10;
		carry = 1 - (sub / 10);
		sub %= 10;
		result.insertHead(sub);
		num1 = num1->prev;
		num2 = num2->prev;
	}
	if (num2)num1 = num2;
	while (num1){
		sub = num1->num - carry;
		sub += 10;
		carry = 1 - (sub / 10);
		sub %= 10;
		result.insertHead(sub);
		num1 = num1->prev;
	}
	if (carry)
		result.insertHead(carry);
	while (result.head && !result.head->num){
		result.deleteHead();
	}
	return result;
}

BigInt BigInt::operator - () const{	// - (负号)的重载
	BigInt result = *this;
	result.symbol = symbol == '+' ? '-' : '+';
	return result;
}

BigInt BigInt::operator = (const BigInt &bigNum){	// = 的重载
	if (this == &bigNum)return *this;

	NumUnit *p;
	temp = head = tail = NULL;
	length = 0;
	p = bigNum.tail;
	while (p){
		insertHead(p->num);
		p = p->prev;
	}
	return *this;
}

bool BigInt::operator < (const BigInt &bigNum) const{	// < 的重载
	if (symbol == '-'){
		if (bigNum.symbol == '+')return true;
		if (length > bigNum.length || (length == bigNum.length && head->num > bigNum.head->num))return true;
	}
	else if (bigNum.symbol == '-')return false;
	else if (length < bigNum.length || (length == bigNum.length && head->num < bigNum.head->num))return true;
	return false;
}

int BigInt::getLength(){
	return length;
}

void BigInt::display(){
	if (head){
		if (symbol == '-')cout << symbol;
		cout << head->num;
		temp = head->next;
	}else{
		cout << 0 << endl;
		return;
	}
	while (temp){
		cout << temp->num;
		temp = temp->next;
	}
	cout << endl;
}

int main(){
	BigInt a, b, sum, sub1, sub2;
	srand((unsigned)time(NULL));
	a.randBigNum();
	b.randBigNum();

	cout << "a     = ";
	a.display();

	cout << "b     = ";
	b.display();

	cout << "-a    = ";
	(-a).display();

	cout << "-b    = ";
	(-b).display();

	BigInt c;
	c = -a;
	cout << "c     = ";
	c.display();

	cout << "a < b = " << (a < b) << endl;
	cout << "b < a = " << (b < a) << endl;

	sum = a + b;
	cout << "a + b = ";
	sum.display();

	sub1 = a - b;
	cout << "a - b = ";
	sub1.display();

	sub2 = b - a;
	cout << "b - a = ";
	sub2.display();

	return 0;
}

bigInt.h

struct NumUnit{
	int num;
	NumUnit *next, *prev;
};
class BigInt{
private:
	NumUnit *head, *tail, *temp;
	int length;
	char symbol;
	void insertHead(int num);
	void deleteHead();
public:
	BigInt();
	BigInt(const BigInt &bigNum);
	BigInt operator + (const BigInt &bigNum) const;
	BigInt operator - (const BigInt &bigNum) const;
	BigInt operator - () const;
	BigInt operator = (const BigInt &bigNum);
	bool operator < (const BigInt &bigNum) const;
	int getLength();
	void randBigNum();
	void display();
	~BigInt();
};