C++primer第5版課後練習習題答案9.52

#include <iostream>
#include <stack>
using namespace std;
int jisuan(string & str)
{
	char op;
	int in2,isum;
	auto pos=str.find_first_not_of("0123456789");
	string sn;
	isum=stoi(str.substr(0,pos));
	cerr<<"isum"<<isum<<endl;
	cout<<"first"<<str.find_first_not_of("0123456789", pos)<<endl;
	cout<<"last"<<str.find_last_of("+-",pos)<<endl;

	while ((pos=(str.find_first_not_of("0123456789", pos)) )!=str.find_last_not_of("0123456789",pos))
	{
		op=str[pos];
		pos++;
			sn = str.substr(pos, str.find_first_not_of("0123456789", pos) - pos);
			cout << "sn" << sn << endl;
			in2 = stoi(sn);
			cout << "in2" << in2 << endl;

			switch (op)
			{
				case '+':
					isum += in2;
					cout << "isum+:" << isum << endl;
					break;

				case '-':
					isum -= in2;
					cout << "isum-" << isum << endl;
					break;

				default:
					cerr << "wrong oprator!" << endl;
					break;
			}


	}
	pos=str.find_last_not_of("0123456789");
	op=str[pos];
	sn=str.substr(pos,str.size()-pos);
	in2=stoi(sn);
	switch (op)
			{
				case '+':
					isum += in2;
					cout << "isum+:" << isum << endl;
					break;

				case '-':
					isum -= in2;
					cout << "isum-" << isum << endl;
					break;

				default:
					cerr << "wrong oprator!" << endl;
					break;
			}

return isum;
}
int main()
{
	stack<char> sc;
	stack<int> si;
	string s;
	char input;

	while (cin >> input)
	{

		if (input == ')')
		{
			char p;

			while (!sc.empty())
			{
				p = sc.top();
				sc.pop();

				if (p == '(')
				{
					break;
				}

				s = p + s;    //p加到前面去 順序就對了

			}

			if (p != '(')
			{
				cerr << "Unmatched )." << endl;
				return -1;
			}
			cout<<"s的表達式:"<<s<<endl;
			int a=jisuan(s);
			s=to_string(a);
			cout<<a<<endl;
			si.push(a);

		}
		else
		{
			sc.push(input);
		}
	}

	while (!sc.empty())
	{
		if (sc.top() == '(')
		{
			cerr << "Unmatched )." << endl;
			return -1;
		}

		s = sc.top() + s;
		sc.pop();
	}
	cout << s << endl;
}