Practice Problems on MEX

MEX of a sequence or an array is the smallest non-negative integer that is not present in the sequence.

Example:

• If we have a sequence S[] = {1,2,0,4,5} then MEX (S) = 3.
• If we have a sequence S[] ={2,0,3,10} then MEX (S) = 1.
• If we have a sequence S[] ={1,2,3,4,5} then MEX (S) = 0.

Note: The MEX of an array of size N cannot be greater than N since the MEX of an array is the smallest non-negative integer not present in the array and array having size N can only cover integers from 0 to N-1. Therefore, the MEX of an array with N elements cannot be greater than N itself.