只支持10以下的计算器

参考代码：

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

/**
return num2 opt num1
*/
int cal(int num1, int num2, char opt)
{
	switch(opt)
	{
	case '+': return num2+num1;
	case '-': return num2-num1;
	case '*': return num2*num1;
	case '/': return num2/num1;
	}
	cout<<"Error in line "<< __LINE__<<" file "<<__FILE__<<endl;
	exit(1);
}

int getPriority(char opt)
{
	switch(opt)
	{
	case '+': return 1;
	case '-': return 1;
	case '*': return 2;
	case '/': return 2;
	case '(': return 0;
	case ')': return 0;
	}
	cout<<"Error in line "<< __LINE__<<" file "<<__FILE__<<endl;
	exit(1);
}

bool comparePriority(char opt1, char opt2)
{
	return getPriority(opt1)<=getPriority(opt2) ? true:false;
}

bool isDigital(const char p)
{
	if(p>='0' && p<='9')
		return true;
	else
		return false;
}

stack<int> Digit;
stack<char> Operator;

int calculator(const char *formula)
{
	if(formula==NULL)
	{
		cout<<"Error in line "<< __LINE__<<" file "<<__FILE__<<endl;
		exit(1);
	}

	const char *p = formula;
	while(*p != '\0') 
	{
		while(*p== ' ')
			p++;
		if(isDigital(*p)) //当前数据是字符
		{
			Digit.push(*p-'0');
			p++;
		}

		else
		{
			if(Operator.empty())
			{
				Operator.push(*p);
				p++;
			}
			else
			{
				char top=Operator.top();
				if(*p!='(' && comparePriority(*p, top) )
				{
					int num1;
					int num2;
					int result;

					while( top!='(' && comparePriority(*p, top) &&!Operator.empty())
					{
						num1=Digit.top();
						Digit.pop();
						num2=Digit.top();
						Digit.pop();
						result=cal(num1,num2,top);
						Digit.push(result);
						Operator.pop();
						if(Operator.empty())
						{
							top=-1;
							break;
						}
							
						else
							top=Operator.top();
						
					}

					if(top=='(')
						Operator.pop();
					else
						Operator.push(*p);
				}
				else
					Operator.push(*p);
				p++; 

			}
		}


	}

	while(!Operator.empty())
	{
		int num1=Digit.top();
		Digit.pop();
		int num2=Digit.top();
		Digit.pop();
		char top=Operator.top();
		int result=cal(num1,num2,top);
		Digit.push(result);
		Operator.pop();
	}
	return Digit.top();
}

int main()
{
	char *p="(1+3)*(5-2)-9";
	cout<<calculator(p)<<endl;
	return 0;
}