4fd800b3a8 2011-02-23        kinaba: 
4fd800b3a8 2011-02-23        kinaba: string add(const string& a, const string& b)
4fd800b3a8 2011-02-23        kinaba: {
4fd800b3a8 2011-02-23        kinaba: 	int n = max(a.size(), b.size()), carry=0;
4fd800b3a8 2011-02-23        kinaba: 	string c(n, '0');
4fd800b3a8 2011-02-23        kinaba: 	for(int i=0; i<n; ++i) {
4fd800b3a8 2011-02-23        kinaba: 		int x = (a.size()<=i ? 0 : a[a.size()-1-i]-'0')
4fd800b3a8 2011-02-23        kinaba: 		      + (b.size()<=i ? 0 : b[b.size()-1-i]-'0') + carry;
4fd800b3a8 2011-02-23        kinaba: 		c[n-1-i] = char('0'+x%10);
4fd800b3a8 2011-02-23        kinaba: 		carry = x/10;
4fd800b3a8 2011-02-23        kinaba: 	}
4fd800b3a8 2011-02-23        kinaba: 	if( carry ) c = char('0'+carry)+c;
4fd800b3a8 2011-02-23        kinaba: 	return c;
4fd800b3a8 2011-02-23        kinaba: }