#include 
#include 
#include 
#define DIGITS 4     bool check_nondigit(char y[])
{
int i;
bool a = false;
for(i=0;i9)
          a = true;
  if(a == true)
        {
           cout << "請輸入0-9的數字" << endl;
       break;
        }
  
}
return a;
}    bool check_repeatdigit(char y[])
{
int i;
bool b = false;
for (i=0;i> y;  //  任何長度字串均可 
        }while(check_repeatdigit(y));
    cout << "請輸入0-9的數字" << endl;
}while(check_nondigit(y));
}    

 
do{
        do{
         cin >> y;  //  輸入"1234" 
        }while(check_repeatdigit(y)); 
         // check_repeatdigit回傳false，因此while loop結束
    cout << "請輸入0-9的數字" << endl;  // 接下來就輸出
}while(check_nondigit(y)); // 回傳false;while loop結束
}

引言: if(y[i]==y[i-1]||y[i]==y[i-2]||y[i]==y[i-3]||y[i]==y[i-4]||y[i]==y[i-5]||y[i]==y[i-6] ||y[i]==y[i-7]||y[i]==y[i-8]||y[i]==y[i-9])

 
bool check_repeatdigit(char y[])
{
    int i,j;
    for (i=0;i<(DIGITS-1);i  )
    {
        for ( j = i 1; j < DIGITS; j   )
        {
            if ( y[i] == y[j] )
            {
                    cout << "有重覆的數字喔！" << endl;
                return true;
            }
        }
    }
    return false;
}