# 平方根

#include <stdio.h>
#include <math.h>
double sqrtNewton(double x) {
	if (x==0) return x;
	double dividend = x;
	double val = x;
	double last;
	do {
		last = val;
		val = (val + dividend / val) * 0.5;
	} while(abs(val - last) > 1e-9); // precision
	return val;
}
int main() {
	double n;
	scanf("%lf", &n);
	printf("Square root of %.3lf = %lf", n, sqrtNewton(n));
}
https://blog.csdn.net/beifangdetian/article/details/120373724



#include <stdio.h>
double sqrt(double n) {
	double i, precision = 0.00001;
	for(i = 1; i*i <=n; ++i);   //Integer part
	for(--i; i*i < n; i += precision);  //Fractional part
	return i;
}
int main() {
	double n;
	scanf("%lf", &n);
	printf("Square root of %.3lf = %.5lf", n, sqrt(n));
}
https://www.yiibai.com/c_examples/square_root_program_in_c.html



//不用平方去計算
#include <stdio.h>
unsigned long sqrt1(double n) {
	int i = 1;
	unsigned long d = 3;
	while (i <= n) {
		i += d; // (i + 1)^2
		d += 2;
	}
	return d / 2 - 1; //Integer part
}
double sqrt2(double n, double i) {
	double precision = 0.00001;
	double p = precision*precision;
	double p1 = p*2, k = i*i, d = 2*i*precision;
	int j=0;
	while (k <= n) {
		k += d + p;
		p += p1;
		j++;
	}
	return i + j*precision; //Fractional part
}
int main() {
	double n;
	scanf("%lf", &n);
	double i = sqrt1(n);   //Integer part
	printf("Square root of %.3lf = %.5lf", n, sqrt2(n,i) );
}