hdu 2051

题意：十进制转二进制

#include<iostream>
using namespace std;
int main()
{
    int n;
    string s;
    while(cin>>n)
    {
        int i=0;
        while(n!=0)
        {
            s[i++]='0'+n%2;
            n=n/2;
        }
        i--;
        for(;i>=0;i--)
        cout<<s[i];
        cout<<endl;
    }
    return 0;
}