// test18.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include<iostream>
#include<string>
#include<list>
using namespace std;
class BigInt{
friend istream& operator>>(istream&, BigInt&);
friend ostream& operator<<(ostream&, BigInt&);
friend BigInt& operator+(BigInt&, BigInt&);
private:
list<int> intLst;
};
/**長整數(shù)加法
基本思路是利用反向迭代器（加法是從地位到高位）實現(xiàn)鏈表并歸
BigInt& operator+(a,b)
while(rIterA!=a.intLst.rend && rIterB!=a.intLst.rend)
c->intLst.push_front((*rIterA+*rIterB+carry)%10); 注意是push_front,從頭結點處入鏈表
if(*rIterA+*rIterB+carry>=10) carry=1 計算是否有進位
else carry=0
rIterA++, rIterB++
while(rIterA!=a.intLst.rend)
c->intLst.push(*rIterA++ + carry)
carry=0;
while(rIterB!=b.intLst.rend)
c->intLst.push(*rIterB++ +carry)
carry=0
return *c
*/
BigInt& operator+(BigInt& a, BigInt& b){
int carry=0;//進位標志
list<int>::reverse_iterator rIterA=a.intLst.rbegin();
list<int>::reverse_iterator rIterB=b.intLst.rbegin();
BigInt* c=new BigInt();
while(rIterA!=a.intLst.rend() && rIterB!=b.intLst.rend()){
c->intLst.push_front((*rIterA+*rIterB+carry)%10);
if((*rIterA+*rIterB+carry)>=10)
carry=1;
else
carry=0;
rIterA++, rIterB++;
}
while(rIterA!=a.intLst.rend()){
c->intLst.push_front(*rIterA++ + carry);//如99+123最高位百位還要進位一次
carry=0;
}
while(rIterB!=b.intLst.rend()){
c->intLst.push_front(*rIterB++ +carry);
carry=0;
}
return *c;
}
istream& operator>>(istream& in, BigInt& bint){
string str;
in>>str;
for(string::iterator iter=str.begin(); iter!=str.end(); iter++){
bint.intLst.push_back(*iter-'0'); //*iter是stirng中每個char對應的ASCII碼
}
return in;
}
ostream& operator<<(ostream& out, BigInt& bint){
for(list<int>::iterator iter=bint.intLst.begin();iter!=bint.intLst.end();iter++)
out<<*iter;
out<<endl;
return out;
}
int main(){
BigInt* a=new BigInt();
BigInt* b=new BigInt();
cout<<"cin>>A: ";
cin>>*a;
cout<<"cin>>B: ";
cin>>*b;
BigInt c=*a+*b;
cout<<c;
system("pause");
}
輸入輸出如下；
cin>>A: 3434685897609608780
cin>>B: 1234234236535634764376
1237668922433244373156