在C++中，itoa 函數并不是標準庫的一部分，因此建議使用其他替代方法

方法1：使用std::to_string

#include<iostream>
#include<string>

int main() {
    int number = 42;
    std::string str_number = std::to_string(number);
    std::cout << "Number as string: "<< str_number<< std::endl;
    return 0;
}

方法2：使用std::ostringstream

#include<iostream>
#include <sstream>
#include<string>

int main() {
    int number = 42;
    std::ostringstream oss;
    oss<< number;
    std::string str_number = oss.str();
    std::cout << "Number as string: "<< str_number<< std::endl;
    return 0;
}

方法3：自定義itoa函數

#include<iostream>
#include<string>
#include<algorithm>

std::string itoa_custom(int value, int base = 10) {
    if (base < 2 || base > 36) {
        throw std::invalid_argument("Invalid base");
    }
    
    if (value == 0) {
        return "0";
    }

    char chars[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    std::string result;
    bool is_negative = value < 0;
    if (is_negative) {
        value = -value;
    }

    while (value != 0) {
        int remainder = value % base;
        result += chars[remainder];
        value /= base;
    }

    if (is_negative) {
        result += '-';
    }

    std::reverse(result.begin(), result.end());
    return result;
}

int main() {
    int number = 42;
    std::string str_number = itoa_custom(number);
    std::cout << "Number as string: "<< str_number<< std::endl;
    return 0;
}

這些方法都可以實現將整數轉換為字符串。選擇最適合你需求的方法。