开平方函数的C语言实现

开平方-二分法实现

//  Created by zscself on 2016/12/20.
#include <stdio.h>
double ssqrt(int v,double t){
	double double_v = (double) v;
	double mid,midd,midSubT,midAddT,low = 0, high = double_v;
	while(1){
		mid = (low + high)/2;
		midd = mid * mid;
		midSubT = mid - t;
		midAddT = mid + t;
		if( midd == v){
			double_v = mid;
		}else if( midd > v ){
			if(midSubT * midSubT < v){
				double_v = mid;
				break;
			}
			high = high-t;
		}else{
			if(midAddT * midAddT > v){
				double_v = mid;
				break;
			}
			low = low+t;
		}
	}
	return double_v;
}
int main(int argc, char *argv[]) {
	printf("%.16f",ssqrt(50000, 0.0001));
	return 0;
}

开平方-牛顿法实现

//  Created by zscself on 2016/12/20.
#include <stdio.h>
double newton(double x,double a){
	double fx = x*x - a;
	double fxD = 2*x;
	double f = x-fx/fxD;
	return f;
}
double ssqrt(int v,double t){
	double f,dv;
	f = dv = (double) v;
	while (1) {
		dv = newton(dv,f);
		if(dv * dv < f && (dv+t)*(dv+t)>f){
			break;
		}
		if(dv * dv > f && (dv-t)*(dv-t)<f){
			break;
		}
	}
	return dv;
}
int main(int argc, char *argv[]) {
	printf("%.16f",ssqrt(50000, 0.0001));
}