reverse()関数による大数加算

#include
#include
#include
using namespace std;
string add(string num1, string num2)
{
	reverse(num1.begin(), num1.end());
	reverse(num2.begin(), num2.end());
	int carry = 0, i = 0, j = 0;
	string ans;
	while(i<num1.size() || j<num2.size())
	{
		int temp;
		if(i<num1.size() && j<num2.size())
		{
			temp = (num1[i] - '0') + (num2[j] - '0') + carry;
			i++;
			j++;
		}
		else if(i<num1.size() && j>=num2.size())
		{
			temp = (num1[i] - '0') + carry;
			i++;
		}
		else if(i>=num1.size() && j<num2.size())
		{
			temp = num2[j] - '0' + carry;
			j++;
		}
		ans.insert(ans.size(), to_string(temp%10));
		carry = temp / 10;
	}
	if(carry > 0) 	ans.insert(ans.size(), to_string(carry));
	reverse(ans.begin(), ans.end());
	return ans;
}
int main()
{
	string a = "123456", b = "456789";
	string result = add(a, b);
	cout<<a<<"+"<<b<<"="<<result;
	return 0;
}