程序代码：

#include <iostream>
#include <string>
using namespace std;


int main(void)
{
    string src, des;
   
    while (cin>>src)
    {
        cout << "长度:" << src.length() << endl;
        if (src.length() >= des.length())
        {
            des = src;
        }
    }

    cout << "最长字符串:" << des << endl;

    return 0;
}