二分搜索开平方

binary_sqrt.c

#include <stdio.h>
#include <math.h>

double m_abs(double num)
{
  return (num < 0 ? -num : num);
}

double bsqrt(double begin, double end, double value, double precision)
{
	// if(begin <= end)
	// 	return 0;
	
	double mid = begin + (end - begin) / 2.0;
	double temp = mid * mid;

	if(m_abs(temp - value) <= precision)
		return mid;
	else if(mid * mid > value)
		return bsqrt(begin, mid, value, precision);
	else 
		return bsqrt(mid, end, value, precision);
}

double m_sqrt(double n)
{
	if(n > 0)
		return bsqrt(0, n, n, 0.00000001);
	else if(m_abs(n) <= 0.00000001)
		return 0;
	else
		return 0;
}

int main(void)
{
	int i = 0;
	for(i = 0; i <= 100; ++i)
	{
		printf("m_sqrt(%d) = %f, sqrt(%d) = %f\n", i, m_sqrt(i), i, sqrt(i));
	}

	return 0;
}