sqrt的实现-牛顿迭代法和二分法对比

1. 二分法实现sqrt()

#include<iostream>
#include<cmath>
using namespace std;
#define eps 1e-2 

float sqrt(float n)
{
    if(n < 0) return 0;
    float mid,last;
    float low,up;
    low = 0,up = n;
    mid=(low + up)/2;
    do{
        if(mid*mid >n)  
            up = mid;
        else    
            low = mid;
        last = mid;
        mid = (up + low)/2;
    }while(abs(mid-last)>eps);
    return mid;
}

int main(){
    cout<<"sqrt(65535) is "<<sqrt(65535)<<endl;
    return 0;
} 

2. 牛顿迭代法实现sqrt()

#include<iostream>
#include<cmath>
using namespace std;
#define eps 1e-2 

float sqrt(float x)
{
    float val = x;//最终
    float last;//保存上一个计算的值
    do
    {
        last = val;
        val =(val + x/val) / 2;
    }while(abs(val-last) > eps);
    return val;
}

int main(){
    cout<<"sqrt(65535) is "<<sqrt(65535)<<endl;
    return 0;
} 

参考链接：

http://blog.csdn.net/qq_26499321/article/details/73724763