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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
+}