// 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, 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 = s.chars().collect(); Self::dfs(0, &graph, &sa); let mut ans: i32 = 0; unsafe { ans = res; } ans } fn dfs(root: usize, graph: &HashMap>, s: &Vec) -> 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 }