Ex02. 頻率計數

(1)
     for ( i = 0 ; i < n ; i ++ )                      n+1
          for ( j = 0 ; j < n ; j ++ )                 n(n+1)
               for ( k = 0 ; k < n ; k ++ )         n²(n+1)
                    a = a + 1 ;                         n³

     頻率計數：2n³+2n²+2n+1


(2)
     i = 1 ;                                                1
     while ( i <= n )                                    n+1
     {
          a = a + 1 ;                                     n
          i ++ ;                                             n
     }

     頻率計數： 3n+2