Przetwarzanie rozwiązania String-Corechef w CPP

#include<iostream>
#include<stack>
using namespace std;

int sum(string exp);
bool IsNumber(char ch);

int main()
{
	string exp;
	int n;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> exp;
		int result = sum(exp);
		cout << result << endl;
	}
	

	return 0;
}
//
int sum(string exp)
{
	stack<char> s;
	int sum = 0;
	for (int i = 0; i < exp.length(); i++)
	{
		if (IsNumber(exp[i]))
		{
			s.push(exp[i] - '0');
			sum += s.top();
		}
		else
		{
			continue;
		}
	}
	return sum;
}
//
bool IsNumber(char ch)
{
	if (ch >= '0' && ch <= '9')
		return true;
	return false;
}
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