sqrt 最后更新于 2025-05-01 18:21:34

```cpp #include <bits/stdc++.h> using namespace std; double my_sqrt(double x) { if (x < 0) { return NAN; } else { double res = x, diff = (res * res - x) / (2 * res); while (diff > 1e-14 * res) { res -= diff; diff = (res * res - x) / (2 * res); } return res; } } int main() { double x; cin >> x; cout << fixed << setprecision(10) << my_sqrt(x); return 0; } ```