Step 1: Divide the number into separate digits:
92378 => 9 2 3 7 8
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 2 => 7
2 to 3 => 1
3 to 7 => 4
7 to 8 => 1
8 to 9 => 1
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
7 => N
1 => C
4 => N
1 => C
1 => C
Step 4: Combine the filters to a string:
N C N C C = NCNCC