1426 Find The Multiple

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 containingno more than 100 decimal digits.InputThe input file may contain multiple test cases. Each line contains a value of n (1 <= n <= 200). A line containing a zero terminates the input.OutputFor 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 themis acceptable.Sample Input

2
6
19
0

Sample Output

10
100100100100100100
111111111111111111

题意：给一个十进制的数n，让你求出一个数m满足m%n=0，并且m这个十进制的数只由01组成（千万别看成二进制）！

题解：直接搜索，一个代表m一个代表位数，不会超long long。

#include <string.h>#include <stdio.h>#define ull long longint n;ull s;int flag;void dfs(ull m , int step) {if(flag || step == 19) return ;if(m%n == 0) {flag = 1;s = m;return ;}dfs(m*10, step+1);dfs(m*10+1,step+1);return ;}int main() {while(~scanf("%d",&n)&&n) {flag = 0;dfs(1, 0);printf("%lld\n",s);}return 0;}