Advent of code 2024

Day 1

Usage:

    rustc d1p1.rs
    cat input.txt | ./d1p1

Part 1:

Parse each line into a pair of ints; store them in a pair of heaps.
Convert heaps into sorted lists. Iterate through them together
and find the absolute difference between each pair of numbers.

Part 2:

Parse each line into a pair of ints; store the first in an array,
place the second into a map that accumulate the number of times
a value is seen.

Iterate through the array, adding the number times the number of
times it was seen in the map.