题解 | #自守数#

#include <stdio.h>
#include <math.h>

int main() {
    int  n =0;
    while(~scanf("%d",&n))
    {
        int i= 0;
        int bit = 0;
        int count = 0;
        int sq = 0;
        for(i=0;i<=n;i++)
        {
            bit = 10;
            int k =i;
            while(k/10!=0)
            {
                bit*=10;
                k/=10;
            }
            sq = (i*i) % bit;
            if(sq == i)
            {
                count++;
            }

        }
        printf("%d",count);
    }
}