C++实现数据保留小数点后两位的常见方法

#include <iostream>
#include <iomanip>
 
int main() {
    double num = 123.45678;
    std::cout << std::fixed << std::setprecision(2) << num << std::endl;
    return 0;
}

#include <cstdio>
 
int main() {
    double num = 123.45678;
    printf("%.2f\n", num);
    return 0;
}

#include <iostream>
#include <sstream>
#include <iomanip>
 
int main() {
    double num = 123.45678;
    std::stringstream ss;
    ss << std::fixed << std::setprecision(2) << num;/*stringstream中
std::stringstream ss;：创建一个stringstream对象ss，用于处理字符串流*/
    std::string result = ss.str();/*使用ss.str()方法将stringstream对象ss中的内容转换为一个std::string类型的字符串，并赋值给变量result_str。此时result_str的值为"3.33"*/
    std::cout << result << std::endl;
    return 0;
}

#include <iostream>
#include <cmath>
 
int main() {
    double num = 123.45678;
    num = std::round(num * 100) / 100;  // 四舍五入到小数点后两位
    std::cout << num << std::endl;
    return 0;
}

#include <iostream>
#include <string>
 
int main() {
    double num = 123.45678;
    std::string str = std::to_string(num);
    size_t dot_pos = str.find('.');
    if (dot_pos != std::string::npos) {
        str = str.substr(0, dot_pos + 3);  // 截取小数点后两位
    }
    std::cout << str << std::endl;
    return 0;
}