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// 2246. Longest Path With Different Adjacent Characters
/*
* you are given a tree (ie. a connected undirected graph that has no cycles)
* rooted at node '0' consisting of 'n' nodes numbered from '0' to 'n - 1'. the
* tree is represented by a 0-indexed array 'parent' of size 'n' where
* 'parent[i]' is the parent of node 'i'. since node 0 is the root, 'parent[0] =
* -1'. you are also given a string 's' of length 'n', where 's[i]' is the
* character assigned to node 'i'. return the legnth of the longest path in the
* tree such that no pair of adjacnet nodes on the path have the same character
* assigned to them.
*/
use std::cmp::max;
use std::collections::HashMap;
struct Solution;
static mut res: i32 = 0;
impl Solution {
pub fn longest_path(parent: Vec<i32>, s: String) -> i32 {
unsafe { res = 0 }
let mut graph = HashMap::new();
for (i, &u) in parent.iter().enumerate() {
if u == -1 {
continue;
}
let u = u as usize;
if !graph.contains_key(&u) {
graph.insert(u, vec![]);
}
graph.entry(u).or_insert(vec![]).push(i);
}
let sa: Vec<char> = s.chars().collect();
Self::dfs(0, &graph, &sa);
let mut ans: i32 = 0;
unsafe {
ans = res;
}
ans
}
fn dfs(root: usize, graph: &HashMap<usize, Vec<usize>>, s: &Vec<char>) -> i32 {
if !graph.contains_key(&root) {
unsafe {
res = max(res, 1);
}
return 1;
}
let (mut a1, mut a2) = (0, 0);
for &v in graph[&root].iter() {
if s[root] == s[v] {
Self::dfs(v, graph, s);
continue;
}
let curr = Self::dfs(v, graph, s);
if curr >= a1 {
a2 = a1;
a1 = curr;
} else if curr > a2 {
a2 = curr
}
}
unsafe {
res = max(res, a1 + a2 + 1);
}
a1 + 1
}
}
fn main() {
let parent1 = vec![-1, 0, 0, 1, 1, 2];
let parent2 = vec![-1, 0, 0, 0];
println!(
"{}",
Solution::longest_path(parent1, String::from("abacbe"))
); //expect: 3
println!("{}", Solution::longest_path(parent2, String::from("aabc"))); //expect: 3
}
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