大数加法

#include<iostream>
#include<string>

using namespace std;

string nGetstrAB(string strA,string strB);
void vOutPut(string strRet);

int main()
{
string strA,strB,strAB;
while(cin >>strA >>strB)
{
strAB=nGetstrAB(strA,strB);
vOutPut(strAB);
}
return 0;
}

string nGetstrAB(string strA,string strB)
{
string strC,strn;
int nCarry,lengthA,lengthB,lengthC,i,sum;
lengthA=strA.length();
lengthB=strB.length(); 

nCarry=0;
if(lengthA>lengthB)
{
strn.resize(lengthA-lengthB,'0');
strB=strn+strB;
        lengthC=lengthA;
strC.resize(lengthC,'0');
for(i=lengthA-1;i>=0;i--)
{
sum=(strA[i]-'0')+(strB[i]-'0')+nCarry;
strC[i]=char(sum%10+'0');
nCarry=sum/10;
}
}
else
{
strn.resize(lengthB-lengthA,'0');
strA=strn+strA;
lengthC=lengthB;
strC.resize(lengthC,'0');
for(i=lengthB-1;i>=0;i--)
{
sum=(strB[i]-'0')+(strA[i]-'0')+nCarry;
strC[i]=char(sum%10+'0');
nCarry=sum/10;
}
}

if(1==nCarry)
{
strC='1'+strC;
}
return strC;
}

void vOutPut(string strRet)
{
cout<<strRet<<endl;
}