Given a positive integer n, write a program to find out a nonzero multiple m of n whose decimal representation contains only the digits 0 and 1. You may assume that n is not greater than 200 and there is a corresponding m containing no more than 100 decimal digits.
Input
The input file may contain multiple test cases. Each line contains a value of n (1 <= n <= 200). A line containing a zero (0) terminates the input.
Output
For each value of n in the input print a line containing the corresponding value of m. The decimal representation of m must not contain more than 100 digits. If there are multiple solutions for a given value of n, any one of them is acceptable.
Sample Input
2
6
19
0
Sample Output
10
100100100100100100
111111111111111111
大致题意：
给个n,找n的十进制倍数，仅有 0 和 1 组成，找一个就行，随便哪一个。
解题思路：
观察以下0，1串：
1
10 11
100 101 110 111
从n=1开始， 重复 n*10 与 n*10+1 ，由此遍历所有01串。
BFS，DFS皆可，以下采用DFS。
#include <iostream>
#include <queue>
#include <cstdio>
using namespace std;
queue<unsigned long long> s;
int n;//输入
unsigned long long temp,p;
void bfs()
{
while(!s.empty())
s.pop();
temp=;
s.push(temp);
while(!s.empty())
{
p=s.front();
s.pop();
if(p%n==)
{
printf("%lld\n",p);//lld！
break;
}
s.push(p*);
s.push(p*+);
}
}
int main(){
while(scanf("%d",&n),n)
{
bfs();
}
return ;
}