编写程序，计算非负数$x$的算术平方根, 要求采用三种实现: 1) for语句; 2) while语句; 3) do-while语句.

1) for语句实现算术平方根：

#include <iostream>
#include <cmath>

using namespace std;

int main() {
    double x;
    cout << "请输入非负数x：";
    cin >> x;
    double sqrt_x = -1; // 初始化sqrt_x为-1
    for (double i = 0; i <= x; i += 0.001) {
        if (abs(i * i - x) < 0.001) { // 判断i是否为平方根
            sqrt_x = i;
            break;
        }
    }
    if (sqrt_x == -1)
        cout << "计算失败！" << endl;
    else
        cout << "算术平方根为：" << sqrt_x << endl;
    return 0;
}

2) while语句实现算术平方根：

#include <iostream>
#include <cmath>

using namespace std;

int main() {
    double x;
    cout << "请输入非负数x：";
    cin >> x;
    double sqrt_x = -1; // 初始化sqrt_x为-1
    double i = 0;
    while (i <= x) {
        if (abs(i * i - x) < 0.001) { // 判断i是否为平方根
            sqrt_x = i;
            break;
        }
        i += 0.001;
    }
    if (sqrt_x == -1)
        cout << "计算失败！" << endl;
    else
        cout << "算术平方根为：" << sqrt_x << endl;
    return 0;
}

3) do-while语句实现算术平方根：

#include <iostream>
#include <cmath>

using namespace std;

int main() {
    double x;
    cout << "请输入非负数x：";
    cin >> x;
    double sqrt_x = -1; // 初始化sqrt_x为-1
    double i = 0;
    do {
        if (abs(i * i - x) < 0.001) { // 判断i是否为平方根
            sqrt_x = i;
            break;
        }
        i += 0.001;
    } while (i <= x);
    if (sqrt_x == -1)
        cout << "计算失败！" << endl;
    else
        cout << "算术平方根为：" << sqrt_x << endl;
    return 0;
}