牛顿迭代法

#include<bits/stdc++.h>
#define int long long
#define PII pair<int,int>
#define ULL unsigned long long
#define all(v) v.begin(), v.end()
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
constexpr int N =  1 * 1e6 + 10,M = 5 * 1e3 + 10,inf = 0x3f3f3f3f;

double cow_function(double n)
{
    constexpr static double eps = 1E-15;
    double x =  1;
    while (1)
    {
        double nx = (x + n / x) / 2;
        if(fabs(x-nx) < eps) break;
        x = nx;
    }
    return x;
}
void solve()
{
    double n;
    cin >> n;
    cout << (int)cow_function(n) << '\n';
}
signed main()
{
    ios::sync_with_stdio(0);cin.tie(nullptr),cout.tie(nullptr);
    int _=1;
    // cin>>_;
    while(_--)
    {
        solve();
    }
    return 0;
}

/**
 *    author: Nijika_jia
 *    created: 2024.10.29 18:42:12
 */

参考答案：

#include<iostream>
#include<cmath>

using namespace std;

int main()
{
    int a;

    cin >> a;
    cout << (int)sqrt(a);

    return 0;
}