求平方根,正根.曾经都不会.昨天看数学,看到了,写了出来.自己又小优化了一下,非常不错.

// squareRoot.cpp -- 2011-08-29-01.04#include "stdafx.h"#include <iostream>double squareRoot (double radicand, double precision) ;int _tmain(int argc, _TCHAR* argv[]){	std ::cout << squareRoot(9, 0.000001) << std ::endl ;	return 0;}double squareRoot (double radicand, double precision){	if (radicand > 0)	{		double squareRoot = radicand / 10 ;		while (squareRoot * squareRoot > radicand)			squareRoot /= 2 ;		double fakePrecision = 0.1; 		while (1)		{			while ((squareRoot + fakePrecision) * (squareRoot + fakePrecision) <= radicand)			{				squareRoot += fakePrecision ;			}			if (fakePrecision > precision)			{				fakePrecision /= 10 ;			}			else			{				return squareRoot ;			}		}	}	else	{		std ::cerr << "Radicand must > 0" << std ::endl ;		return 0 ;	}}