MongoDB聚合运算符：$firstN

华为机考：HJ107 求解立方根

#include<iostream>
#include<iomanip>
using namespace std;

int main() {
    double num, val;
    cin >> num;
    for(val = -20; val <= 20; val += 0.01){
        if(num - val * val * val <= 1e-8){
            break;
        }
    }
    cout << fixed << setprecision(1) << val << endl;
    return 0;
}

华为机考：HJ107 求解立方根