double double_int(double a)
{//去除double型数据的小数部分，保留整数部分
	double i = 1, power = 1, a1 = 0;//i为a的整数位数，power为整数部分最高位权重
	for (double n = a / 10; n >= 1; i++)//求i(整数位数)
		n /= 10;
	if (i < 10) return int(a);
	else
	{ 
		for (int j = 1; j < i; j++)//求power
			power *= 10;
		for (int j = 0; j < i; power /= 10, j++)//求a的整数部分
			a1 += int((a - a1) / power) * power;
		return a1;
	}
}