字符串中的數字相加

class addNum
{
public:
	int addStrNum(string str)
	{
		int j,num,sum=0;
		for (int i=0;i<str.length();)
		{
			if (str[i]<='9'&&str[i]>='0')
			{
				num=(str[i]-'0');
				++i;
				while(i<str.length()&&str[i]<='9'&&str[i]>='0')
				{
					num=num*10+(str[i]-'0');
					++i;
				}
				sum+=num;
			}
			else
			{
				i++;
			}
		 }
			return sum;
	  }	
	
};