C语言，如何将字符串中的数字单独转为浮点数?

字符串：You will pay $687.71 every month

请问如何如何输出687.71的浮点数？

参考代码如下，将你的字符串输入到窗口即可输出： 

#include <cstdlib>
#include <math.h>
#include <stdio.h>
int main()
{
	char str[1000];
	gets(str);  


	char num[100] = {0};
	int i = 0;
	for (; str[i] != '\0'; i++)
	{
		if (str[i] == '$')
		{
			int j = i + 1;
			int k = 0;
			for (; str[j] != '\0'; j++)
			{
				if (str[j] != ' ')
				{
					num[k++] = str[j];
				}
				else
				{
					num[k] = '\0';
					break;
				}
			}
		}
	}

	double dnum = 0.0;
	i = 0;
	int j = 0;
	for ( i = 0; num[i] != '\0'; i++)
	{
		if (num[i] == '.')
		{
			j = i;
		}
	}
	i = j - 1;
	int k = 0;
	for (; i >= 0; i--)
	{
		dnum += (num[i] - '0') * pow(10, k);
		k++;
	}

	i = j + 1;
	k = 1;
	for (; num[i] != '\0'; i++)
	{
		dnum += (num[i] - '0') / pow(10, k);
		k++;
	}

	printf("%f", dnum);

	return 0;
}

用stringstream

你具体看这个吧，这个写的非常全面https://www.baidu.com/link?url=Iaw_xMLYXtl6vIrTUPlBcdxxJAGyPrUQRsI3Xkp3uHjgVSdzlAOd5SEw13zPjPnat3uXXkVaiO-zPm6Tc6p7iq&wd=&eqid=df90474a002d1d940000000360d7e6cf

你复制进入这个网址就行了，保你学会stringstream