字符串中找出连续最长的数字串

读入一个字符串str，输出字符串str中的连续最长的数字串。

#include<iostream>
#include<string>

using namespace std;

int main()
{
	string str;
	cin >> str;
	int max_num = 0,cur_num=0;
	int start = 0;
	string s = "";
	int cur = 0;
	while (cur < str.size())
	{
		while (str[cur] >= '0'&&str[cur] <= '9')
		{
			cur_num++;
			cur++;
		}
		if (cur_num>max_num)
		{
			max_num = cur_num;
			start = cur - cur_num;
		}
		cur_num = 0;
		cur++;
	}
	s = str.substr(start, max_num);//截取字符串
	cout << s << endl;

	return 0;
}