light oj 1078 - Integer Divisibility

1078 - Integer Divisibility
Time Limit: 2 second(s) Memory Limit: 32 MB

If an integer is not divisible by 2 or 5, some multiple of that number in decimal notation is a sequence of only a digit. Now you are given the number and the only allowable digit, you should report the number of digits of such multiple.

For example you have to find a multiple of 3 which contains only 1's. Then the result is 3 because is 111 (3-digit) divisible by 3. Similarly if you are finding some multiple of 7 which contains only 3's then, the result is 6, because 333333 is divisible by 7.

Input

Input starts with an integer T (≤ 300), denoting the number of test cases.

Each case will contain two integers n (0 < n ≤ 106 and n will not be divisible by 2 or 5) and the allowable digit (1 ≤ digit ≤ 9).

Output

For each case, print the case number and the number of digits of such multiple. If several solutions are there; report the minimum one.

Sample Input

Output for Sample Input

3

3 1

7 3

9901 1

Case 1: 3

Case 2: 6

Case 3: 12

题意:给出 n和m,让判断多少位的m可以整除n(每一位的数值都为m,如果当前的位数不能整除n则再加上一位)如:3   1意思是多少个1可以整除3显然111可以整除3,所以就是三位,输出3

小技巧:令ans=m 让ans对n取余为ans(覆盖原来的值),每次让ans=ans*10+m(因为不能整除所以增加位数)直到可以整除   原理大概是除法的同余定理吧

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<algorithm>
#include<math.h>
#define LL long long
#define DD double
#define MAX 10000
using namespace std;
int main()
{
int t;
int n,m,j,i;
LL ans;
scanf("%d",&t);
int k=1;
while(t--)
{
scanf("%d%d",&n,&m);
printf("Case %d: ",k++);
ans=m;
int sum=1;
while(ans%n)
{
ans=ans%n;
ans=ans*10+m;
sum++;
}
printf("%d\n",sum);
}
return 0;
}

  

  

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