c++ - 同一程序每次返回不同的输出？

Question

每次运行程序时，使用完全相同的值(直径为 25，深度为 5)，我都会得到不同的 water_price 值，但我不确定为什么。

一些结果:

$6.62256e+07 is the total cost.
$0 is the total cost.
$2.43411e-27 is the total cost.

我不知道我是否正在处理内存中的值彼此不能很好地配合，不刷新或什么。

为什么每次运行该程序时结果都不同？

#include <iostream>

#define PI 3.1416
#define WATER_COST 1.80

using std::cout;
using std::cin;
using std::endl;

int main() {

    float pool_diameter, pool_depth;
    float pool_radius = pool_diameter / 2;
    float pool_volume_sq_inches = (PI * pool_radius * pool_radius * pool_depth) * 1728;
    float pool_gallons = pool_volume_sq_inches / 231;
    float water_price = (pool_gallons / 748) * WATER_COST;

    cout << "Enter the pool diameter: ";
    cin >> pool_diameter;
    cout << "\nEnter the pool depth: ";
    cin >> pool_depth;

    cout << "\n$" << water_price << " is the total cost." << endl;

    return 0;
}

Answer 1

看看我们首先需要如何声明变量，然后当您要求输入时，它将存储在这些变量中，然后您可以继续进行所需的计算。

#include <iostream>
#define PI 3.1416
#define WATER_COST 1.80

using std::cout;
using std::cin;
using std::endl;

int main() {

    float pool_diameter = 0.0;
    float pool_depth = 0.0;

    cout << "Enter the pool diameter: ";
    cin >> pool_diameter;
    cout << "\nEnter the pool depth: ";
    cin >> pool_depth;


    float pool_radius = pool_diameter / 2;
    float pool_volume_sq_inches = (PI * pool_radius * pool_radius * pool_depth) * 1728;
    float pool_gallons = pool_volume_sq_inches / 231;
    float water_price = (pool_gallons / 748) * WATER_COST;


    cout << "\n$" << water_price << " is the total cost." << endl;

    return 0;
}