求平方根的方法(牛顿迭代法和二分法)

#include <iostream>
#include <cstdlib>
#include <cmath>
using namespace std;

double _sqrt(double val, double x)          //牛顿迭代法
{
    if(abs(x*x - val) < 0.00001){return x;}
    else{
        x = (x + val/x)/2;
        return _sqrt(val, x);
    }
}


double sqrt_Rec(double val)
{
    return _sqrt(val, 1.0);
}


double sqrt_2(double val)        //二分法
{
    double left = 0;
    double right = val > 1.0?val: 1.0;

    double mid = (left + right)/2;
    while(abs(mid*mid - val) > 0.00001){
        if( mid*mid - val > 0){
            right = mid;
        }else{
            left = mid;
        }
        mid = (left + right)/2;
    }
    return mid;
}


int main()
{
    double num;
    while(cin >> num){
        cout << sqrt_2(num) << endl;
    }
}