C++的ceil、floor和round用法解读

#include <cmath>
#include <iostream>

int main() {
    double x = 3.2;
    double y = -2.7;

    std::cout << std::ceil(x) << std::endl;  // 输出 4.0
    std::cout << std::ceil(y) << std::endl;  // 输出 -2.0

    return 0;
}

#include <cmath>
#include <iostream>

int main() {
    double x = 3.7;
    double y = -2.3;

    std::cout << std::floor(x) << std::endl;  // 输出 3.0
    std::cout << std::floor(y) << std::endl;  // 输出 -3.0

    return 0;
}

#include <cmath>
#include <iostream>

int main() {
    double x = 3.4;
    double y = 3.6;
    double z = -2.5;

    std::cout << std::round(x) << std::endl;  // 输出 3.0
    std::cout << std::round(y) << std::endl;  // 输出 4.0
    std::cout << std::round(z) << std::endl;  // 输出 -2.0（注意：-2.5 四舍五入为 -2）

    return 0;
}

int ceil_division(int a, int b) {
    return (a + b - 1) / b;
}

int x = 7, y = 3;
int ceil = (x + y - 1) / y;  // ceil = 3（因为 7/3 ≈ 2.333，向上取整得 3）

int floor_division(int a, int b) {
    return a / b;
}

int x = 7, y = 3;
int floor = x / y;  // floor = 2（因为 7/3 ≈ 2.333，向下取整得 2）

int round_division(int a, int b) {
    return (a + b / 2) / b;
}

int x = 7, y = 3;
int rounded = (x + y / 2) / y;  // rounded = 2（因为 7/3 ≈ 2.333，四舍五入得 2）

int ceil_val = static_cast<int>(std::ceil(3.2));  // ceil_val = 4
int floor_val = static_cast<int>(std::floor(3.7));  // floor_val = 3
int round_val = static_cast<int>(std::round(3.6));  // round_val = 4

g++ program.cpp -o program -lm