题解 | #挑7#

#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#define max 30000
#define row 100
#define col 1001

//2021/7/3 - 18:28
//2021/7/3 - 18:39


int main()
{
   int i, j, k, x;

   while (scanf("%d", &x) != EOF)
   {
      for (i = 7, j = 0; i <= x; i++)
      {
         k = i;

         if (i % 7 == 0)
         {
            j++;
         }
         else
         {
            while (k != 0)//check if contain 7
            {
               if ((k % 10) == 7)
               {
                  j++;
                  break;
               }
               k /= 10;
            }
         }
      }

      printf("%d\n", j);
   }


   return 0;
}