C++中后缀运行时错误的中缀

#include <iostream>
#include <stack>
#include <string>
#include <vector>

int precedence(char op) {
    if (op == '+' || op == '-') return 1;
    if (op == '*' || op == '/') return 2;
    return 0;
}

std::vector<std::string> infixToPostfix(const std::string& infix) {
    std::stack<char> operators;
    std::vector<std::string> postfix;
    std::string number;

    for (char ch : infix) {
        if (isdigit(ch)) {
            number += ch;
        } else {
            if (!number.empty()) {
                postfix.push_back(number);
                number.clear();
            }
            if (ch == '(') {
                operators.push(ch);
            } else if (ch == ')') {
                while (!operators.empty() && operators.top() != '(') {
                    postfix.push_back(std::string(1, operators.top()));
                    operators.pop();
                }
                operators.pop(); // Remove '(' from stack
            } else {
                while (!operators.empty() && precedence(operators.top()) >= precedence(ch)) {
                    postfix.push_back(std::string(1, operators.top()));
                    operators.pop();
                }
                operators.push(ch);
            }
        }
    }

    if (!number.empty()) {
        postfix.push_back(number);
    }

    while (!operators.empty()) {
        postfix.push_back(std::string(1, operators.top()));
        operators.pop();
    }

    return postfix;
}

int main() {
    std::string infix = "a+b*c";
    std::vector<std::string> postfix = infixToPostfix(infix);

    for (const std::string& token : postfix) {
        std::cout << token << " ";
    }

    return 0;
}