//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 != '