二分查找的应用--求一个数的平方根sqrt

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一、二分查找

二分查找算法

二、代码

#include 
#include 

#define PRECISION 0.0000001

double Sqrt(double n)
{
	double dblRet = 0.0;

	double dblLow = 0.0;
	double dblHigh = n;
	double dblMiddle = 0.0;


	// 判断当前数所处的最小整数区间
	/*double i = 0;
	while (i <= n)
	{
		if (i * i == n)
		{
			return i;
		}
		if (i * i > n)
		{
			break;
		}

		i = i + 1.0;
	}
	dblHigh = i;*/

	while (dblLow <= dblHigh)
	{
		dblMiddle = dblLow + (dblHigh - dblLow) / 2;

		// 浮点数两数相等的判断，这里也就是判断（dblMiddle^2 == n）
		if ((dblMiddle * dblMiddle - n < (PRECISION))
			&& (dblMiddle * dblMiddle - n > -(PRECISION)))
		{
			dblRet = dblMiddle;
			break;
		}
		else if (dblMiddle * dblMiddle > n)
		{
			dblHigh = dblMiddle - PRECISION / 1000;   // 这里增加或减少的值越小越精确
		}
		else if (dblMiddle * dblMiddle < n)
		{
			dblLow = dblMiddle + PRECISION / 1000;
		}

	}

	return dblRet;
}


int main()
{
	double n = 0.0;

	int i = 0;
	for (i = 0; i < 100; i++)
	{
		printf("Sqrt(%-02d)=%0.6lf \t math:sqrt(%-02d)=%0.6lf\r\n", i, Sqrt(i), i, sqrt(i));
	}

	getchar();
	return 0;
}

三、运行结果

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