Index matching algorithm without hash-based data structures?

Question

I am programming in C, so I do not want to implement a hash-based datastructure such as a hashset or hashmap/dictionary. However, I need to solve the following task in linear time.

Given two arrays $a$ and $b$ which contain the same set of distinct integers, determine for every element of $a$ the index of the same element in $b$.

For example, if $a=[9,4,3,7]$ and $b=[3,4,7,9]$, then the output should be $[3,1,0,2]$.

Note that this becomes a very easy task when you have a hashset, because you can simply store for every element in $b$ the index, and then query the hashmap for every element of $a$.

So my question is whether there is a linear algorithm for this task that does not use any hashsets.