51nod 1035 最长的循环节

#include <bits/stdc++.h>
using namespace std;

const int MAXN = 1010;
int res[MAXN];

int mod_pow(int a, int b, int m)
{
int res = 1;
while(b)
{
if(b&1) res = res*a%m;
a = a*a%m;
b >>= 1;
}
return res;
}

int calc(int num)
{
while(num%2 == 0) num/=2;
while(num%5 == 0) num/=5;
if(num == 1) return 1;
int i = 1;
while(mod_pow(10,i,num) != 1) i++;
return i;
}

void init()
{
int temp;
int maxn = 0;
for(int i = 1; i < MAXN; ++i)
{
temp = calc(i);
if(temp > maxn)
{
maxn = temp;
res[i] = i;
}
else
res[i] = res[i-1];

}
}

int main()
{
init();
int n;
cin >> n;
cout << res
<<endl;
return 0;
}