I don't understand this question

can you tell me how to solve this question

@sksumitkumardiwaker,
We know everytime a number repeats, it is given a new hash value, which is equal to the number of distinct numbers occurred till now. So we can just store the last occurrences of all the numbers and assign the values incrementally, in increasing order of the positions of their last occurrences.

you can also watch this for reference: