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|
use std::io::{self, BufRead};
use itertools::Itertools;
fn read_input() -> Vec<(String, String)> {
let stdin = io::stdin();
stdin.lock().lines()
.map(|line| line.unwrap().split(')').map(|s| s.to_string())
.next_tuple().unwrap()
).collect()
}
#[derive(Clone, Debug)]
struct Tree {
name: String,
children: Vec<Tree>,
}
impl Tree {
fn new(name: &str) -> Self {
Tree {
name: name.to_string(),
children: Vec::new(),
}
}
fn new_with_one(name: &str, tree: Tree) -> Self {
Tree {
name: name.to_string(),
children: vec![tree],
}
}
fn join(&mut self, mut tree:Tree) -> bool {
if self.name == tree.name {
self.children.append(&mut tree.children);
true
} else {
for c in &mut self.children {
if c.contains(&tree.name) {
c.join(tree);
return true;
}
}
false
}
}
fn contains(&self, needle:&str) -> bool {
if &self.name == needle {
return true;
}
for c in &self.children {
if c.contains(needle) {
return true;
}
}
false
}
fn orbit_count(&self) -> usize {
fn orbit_count_internal(t: &Tree, s:usize) -> usize {
let mut n = s;
for c in &t.children {
n += orbit_count_internal(c, s + 1);
}
n
}
orbit_count_internal(self, 0)
}
fn find_distance(&self, to: &str) -> Option<usize> {
fn find_distance_internal(t:&Tree, p: &str, s:usize) -> usize {
for c in &t.children {
if c.contains(p) {
return find_distance_internal(c, p, s + 1);
}
}
s
}
if self.contains(to) {
Some(find_distance_internal(self, to , 0))
} else {
None
}
}
fn last_common_ancestor(&self, from: &str, to: &str) -> Option<Tree> {
fn ancestor_internal(t: &Tree, from: &str, to: &str) -> Option<Tree> {
if t.contains(from) && t.contains(to) {
for c in &t.children {
if c.contains(from) && c.contains(to) {
return ancestor_internal(c, from, to);
}
}
Some(t.clone())
} else {
None
}
}
ancestor_internal(self, from, to)
}
}
fn build_tree(orbit_map: Vec<(String, String)>) -> Option<Tree> {
let mut trees:Vec<Tree> = Vec::new();
for (parent, child) in &orbit_map {
let mut found = false;
for t in &mut trees {
if t.contains(parent) {
let newtree = Tree::new_with_one(parent, Tree::new(child));
found = t.join(newtree);
break;
}
}
if ! found {
let newtree = Tree::new_with_one(parent, Tree::new(child));
trees.push(newtree);
}
}
while {
let last_len = trees.len();
let mut i = 0;
while i < trees.len() {
let mut one = trees.remove(i);
let mut j = 0;
while j < trees.len() {
let mut two = trees.remove(j);
if one.contains(&two.name) {
one.join(two);
} else if two.contains(&one.name) {
two.join(one);
one = two;
} else {
trees.push(two);
}
j += 1;
}
trees.push(one);
i += 1;
}
trees.len() != last_len
} {}
if trees.len() == 1 {
trees.pop()
} else {
None
}
}
fn first_puzzle(tree: &Tree) {
println!("Solution to first part: {}.", tree.orbit_count());
}
fn second_puzzle(tree: &Tree, from: &str, to: &str) {
let junction = tree.last_common_ancestor(from, to);
let distance = match junction {
Some(j) =>
j.find_distance(from).expect("Not reachable.") +
j.find_distance(to).expect("Not reachable.") - 2,
None => panic!("No path between {} and {}.", from, to),
};
println!("Solution to second part: {}.", distance);
}
fn main() {
let orbit_map = read_input();
let tree = build_tree(orbit_map.clone());
match &tree {
Some(t) => {
first_puzzle(t);
second_puzzle(t, "YOU", "SAN");
},
None => panic!("Could not make sense of orbit map.")
}
}
|
