题解 | #自守数#

#include <iostream>
#include <math.h>

using namespace std;
int main()
{
    int n;
    while(cin>>n)
    {
        if(n == 0)
        {
            cout<<"1"<<endl;
            continue;
        }
        if(n == 1)
        {
            cout<<"2"<<endl;
            continue;
        }
        int num = 2;
        int tmp = 0;
        for(int i=2; i<=n; i++)
        {
            int j = i;
            while(j)
            {
                tmp ++;
                j /= 10;              
            }
            if(i*(i-1)%(int)pow(10,tmp) == 0)
            {
                num++;
            }
            tmp = 0;
        }
        cout<<num<<endl;
    }
    return 0;
}