UVa 10474 - Where is the Marble?

Summary
Given N marbles which are numbered between 1..10000. The numbers may contain duplicates and not ordered.

You have to sort the marbles numbers in non decreasing order.

For each Q queries, you have to determine the position of the specified marbles in the sorted marble numbers.

Explanation
Let

count[X] be the number of occurrence of marble X

Using the information on array count[], we can create another array (it's basically a counting sort):

marble[position], the marble number which resides in position position of the sorted marbles

Since we want the inverse of the marble[position], we just loop 1..10000 to make an inverse array:

position[marble], the position of the marble in the sorted marbles

The complexity of having the array marble[position] and position[marble] is O(2*10000).

After having the array position[marble] we can answer all the queries easily in O(1).