python/TangDou/AcWing/BinarySearch/790_2.cpp

#include <bits/stdc++.h>
using namespace std;

/*
浮点数不能太大，10000>=a>=-10000
*/

double sqrt(int n) {
    double x = n;
    for (int i = 1; i <= 100; i++) x = (x * x + n) / (2 * x);
    return x;
}

double sqrt3(int n) {
    double x = n;
    for (int i = 1; i <= 100; i++) x = (2 * x * x * x + n) / (3 * x * x);
    return x;
}

double sqrt4(int n) {
    double x = n;
    for (int i = 1; i <= 100; i++) x = (3 * x * x * x * x + n) / (4 * x * x * x);
    return x;
}

double sqrt5(int n) {
    double x = n;
    for (int i = 1; i <= 100; i++) x = (4 * x * x * x * x * x + n) / (5 * x * x * x * x);
    return x;
}

int main() {
    // 求n的平方根和立方根
    double n;
    cin >> n;

    // 平方根
    printf("%.6lf\n", sqrt(n));

    // 立方根
    printf("%.6lf\n", sqrt3(n));

    // 4次方根
    printf("%.6lf\n", sqrt4(n));

    // 5次方根
    printf("%.6lf\n", sqrt5(n));

    return 0;
}