Valid Anagram - Algorithm

Two ways to solve this:

$1.$ Build frequency maps for both strings, compare them. Time: $O(n)$, Space: $O(k)$ where $k$ is alphabet size.

$2.$ Build one frequency map for $s$, then decrement for each character in $t$. If any count goes negative or non-zero counts remain, not an anagram. Both work. The second uses less space if you're careful.