大数加法

C++

#include <bits/stdc++.h>
#define rep( x,a,b )  for ( int x = a; x != b; ++x )
#define clr( x,val )   memset( x,val,sizeof(x) )
using namespace std;

string bigNumAdd( string str1,string str2 )
{
    char rs[10000];
    clr( rs,0 );
    int maxLength = max( str1.size(),str2.size() );
    reverse( str1.begin(),str1.end() );
    reverse( str2.begin(),str2.end() );
    int x   = 0;
    int i   = 0;
    for (; i < maxLength; ++i )
    {
        int a   = 0;
        int b   = 0;
        if ( i <= str1.size() - 1 )
        {
            a = str1.at( i ) - '0';
        }
        if ( i <= str2.size() - 1 )
        {
            b = str2.at( i ) - '0';
        }
        int total = a + b + x;
        rs[i]   = (char) (total % 10 + '0');
        x   = total / 10;
    }
    if ( x > 0 )
        rs[i] = x;
    string end( rs );


    reverse( end.begin(),end.end() );
    printf( "%s",end.c_str() );
    return(end);
}


int main()
{
    bigNumAdd( "999999999999932132132132132132199","213213123123213213213213123213213213123" );
    return(0);
}