后缀表达式计算（代码）

#include <iostream>
#include <stack>

using namespace std;

int Priority(char ch)
{
	switch(ch)
	{
		case '(':
			return 3;
		case '*':
		case '/':
			return 2;
		case '+':
		case '-':
			return 1;
		default:
			return 0;
	}
}

int main()
{
	char opt[100] = {0};
	stack<int> stack_num;     //保存操作数
	stack<char> stack_opt;    //保存操作符
	int i = 0, tmp = 0;
	char option;
	int num1, num2;
	
	cout << "Please input : " << endl;
	cin >> opt;

	while (opt[i] != '\0' || stack_opt.empty() != true)
	{
		if (opt[i] >= '0' && opt[i] <= '9')     //操作数进栈
		{
			tmp = tmp * 10 + opt[i] - '0';
			i++;
			if (opt[i] < '0' || opt[i] > '9')
			{
				stack_num.push(tmp);
				tmp = 0;
			}
		}
		else                                   //操作符
		{
			if (stack_opt.empty() || (stack_opt.top() == '(' && opt[i] != ')') || 
				Priority(opt[i]) > Priority(stack_opt.top()))   //操作符进栈
			{
				stack_opt.push(opt[i]);
				i++;
				continue;
			}

			if (stack_opt.top() == '(' && opt[i] == ')')   //操作符出栈不计算
			{
				stack_opt.pop();
				i++;
				continue;
			}

			if ((opt[i] == '\0' && stack_opt.empty() != true) || 
				opt[i] == ')' && stack_opt.top() != '(' || 
				Priority(opt[i]) <= Priority(stack_opt.top()))  //出栈 计算
			{
				option = stack_opt.top();
				stack_opt.pop();
				switch(option)
				{
					case '+':
						num1 = stack_num.top();
						stack_num.pop();
						num2 = stack_num.top();
						stack_num.pop();
						stack_num.push(num1 + num2);
						break;
					case '-':
						num1 = stack_num.top();
						stack_num.pop();
						num2 = stack_num.top();
						stack_num.pop();
						stack_num.push(num2 - num1);
						break;
					case '*':
						num1 = stack_num.top();
						stack_num.pop();
						num2 = stack_num.top();
						stack_num.pop();
						stack_num.push(num1 * num2);
						break;
					case '/':
						num1 = stack_num.top();
						stack_num.pop();
						num2 = stack_num.top();
						stack_num.pop();
						stack_num.push(num2 / num1);
						break;
				}
			}
		}
	}

	cout << "result : " << stack_num.top() << endl;

	return 0;
}