Town Judge - Graph Translation

The trust relationships form a directed graph where each edge $(a, b)$ means person $a$ trusts person $b$. The town judge is the vertex with in-degree $n-1$ and out-degree $0$.

You can represent this using an array of in-degrees and out-degrees. Each trust pair increments one counter and decrements another.

This translation is the hard part. Once you see it is a degree-counting problem, the code writes itself.