parallel-letter-frequency: Using usize as the input and output types
use std::collections::HashMap;
-pub fn frequency(input: &[&str], worker_count: i32) -> HashMap<char, u32> {
+pub fn frequency(input: &[&str], worker_count: usize) -> HashMap<char, usize> {
unimplemented!(
"Count the frequency of letters in the given input '{:?}'. Ensure that you are using {} to process the input.",
input,
