devc++用中缀表达式求值

以下是使用栈实现中缀表达式求值的示例代码：

#include <iostream>
#include <stack>
#include <string>
#include <cctype>

using namespace std;

// 定义操作符的优先级
int priority(char op) {
    if (op == '+' || op == '-') {
        return 1;
    } else if (op == '*' || op == '/') {
        return 2;
    } else {
        return 0;
    }
}

// 计算两个数的结果
int calculate(int num1, int num2, char op) {
    if (op == '+') {
        return num1 + num2;
    } else if (op == '-') {
        return num1 - num2;
    } else if (op == '*') {
        return num1 * num2;
    } else {
        return num1 / num2;
    }
}

// 中缀表达式求值
int evaluate(string expression) {
    stack<int> numStack; // 存放操作数的栈
    stack<char> opStack; // 存放操作符的栈

    for (int i = 0; i < expression.length(); i++) {
        char ch = expression[i];
        if (isdigit(ch)) { // 如果是数字，将其转换为整数并压入操作数栈
            int num = ch - '0';
            while (i + 1 < expression.length() && isdigit(expression[i + 1])) {
                num = num * 10 + (expression[i + 1] - '0');
                i++;
            }
            numStack.push(num);
        } else if (ch == '(') { // 如果是左括号，将其压入操作符栈
            opStack.push(ch);
        } else if (ch == ')') { // 如果是右括号，弹出操作符栈中的操作符并计算，直到遇到左括号
            while (opStack.top() != '(') {
                char op = opStack.top();
                opStack.pop();
                int num2 = numStack.top();
                numStack.pop();
                int num1 = numStack.top();
                numStack.pop();
                numStack.push(calculate(num1, num2, op));
            }
            opStack.pop(); // 弹出左括号
        } else if (ch == '+' || ch == '-' || ch == '*' || ch == '/') { // 如果是操作符
            while (!opStack.empty() && opStack.top() != '(' && priority(opStack.top()) >= priority(ch)) {
                char op = opStack.top();
                opStack.pop();
                int num2 = numStack.top();
                numStack.pop();
                int num1 = numStack.top();
                numStack.pop();
                numStack.push(calculate(num1, num2, op));
            }
            opStack.push(ch);
        }
    }

    while (!opStack.empty()) { // 处理剩余的操作符
        char op = opStack.top();
        opStack.pop();
        int num2 = numStack.top();
        numStack.pop();
        int num1 = numStack.top();
        numStack.pop();
        numStack.push(calculate(num1, num2, op));
    }

    return numStack.top(); // 返回最终结果
}

int main() {
    string expression = "3+4*5-(6+7)*8/9";
    int result = evaluate(expression);
    cout << "The result of " << expression << " is " << result << endl;
    return 0;
}