题解 | ISBN号码

#include <stdio.h>

int main() 
{
    char num[14];
    gets(num);
    int k=((num[0]-'0')*1+(num[2]-'0')*2+(num[3]-'0')*3+(num[4]-'0')*4+(num[6]-'0')*5+(num[7]-'0')*6+(num[8]-'0')*7+(num[9]-'0')*8+(num[10]-'0')*9)%11;
    if(k==10)
    {
        if(num[12]=='X')
        printf("Right\n");
        else
         {
             num[12]='X';
             puts(num);
         }
    }
    else 
    {
      if(k+'0'==num[12])
       printf("Right\n");
      else
      {
        num[12]=k+'0';
        puts(num);
      }
    }
    
    return 0;
}