题解 | #挑7#

#include<stdio.h>


int Contain7(int x)
{
    if(x == 0)
        return 0;
    if(x%10 == 7)
        return 1;
    return Contain7(x/10);
}

int main()
{
    int n;
    int cnt = 0;
    int i = 0;
    
    while(scanf("%d",&n)!=EOF)
    {
        for(i=7;i<=n;i++)
        {
            if(i%7==0)
            {
                cnt++;
            }
            else if(Contain7(i))
            {
                cnt++;
            }   
        }
        printf("%d",cnt);
        
    }
    
    
    return 0;
}