算法:循環數規律,若某數a是循環數, 則a*(n+1)所得的結果全是9
#include <iostream>
#include <string.h>
using namespace std;
char str[100];
int main()
{
while (cin >> str)
{
bool flag = true;
int n = strlen(str) + 1;
int b = 0; // 進位
for (int i=n-2; i>=0; i--)
{
int a = (str[i]-'0')*n + b;
b = a / 10;
int c = a % 10;
if (c != 9)
{
flag = false;
break;
}
}
(flag)? cout << str << " is cyclic" << endl : cout << str << " is not cyclic" << endl;
}
}