//编写函数实现库函数atof

#include <stdio.h>

#include <assert.h>

#include <ctype.h>

#include <math.h>

double calculate(const char *src, int flag)

{

	double num = 0.0;

	int n = 0;

	int count = 0;

	while (*src)

	{

		if ((*src >= '0') && (*src <= '9'))//推断输⼊入是否为⾮非数组字符

		{

			num = num * 10 + (*src - '0');

			src++;

			if (n)

			{

				count++;

			}

		}

		else if (*src == '.')

		{

			n = 1;

			src++;

		}

		else

		{

			num = 0;

			break;

		}

	}

	if (n)

	{

		num = num / powl(10,count);

	}

	return flag * num;

}

double str_to_int(const char *str)

{

	double num = 0.0;

	int flag = 1;

	if (str != NULL && *str != '\0')

	{

		while (isspace(*str))

		{

			str++;

		}

		if (*str == '+')

			str++;

		else if (*str == '-')

		{

			str++;

			flag = -1;

		}

		 if (*str != '\0')

		{

			num = calculate(str, flag);

		}

	}

	return num;

}

int main()

{

	printf("%f\n", str_to_int(" +23.45"));

	printf("%f\n", str_to_int(" -2.345"));

	printf("%f\n", str_to_int("+234.5"));

	printf("%f\n", str_to_int("-2345.44"));

	printf("%f\n", str_to_int("2345"));

	printf("%f\n", str_to_int("-1111.11"));

	printf("%f\n", str_to_int(""));

	printf("%f\n", str_to_int("123ab"));

	return 0;

}