Given the root of a binary tree and two integers p and q, return the distance between the nodes of value p and value q in the tree.
The distance between two nodes is the number of edges on the path from one to the other.
Example 1:
Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 0 Output: 3 Explanation: There are 3 edges between 5 and 0: 5-3-1-0.
Example 2:
Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 7 Output: 2 Explanation: There are 2 edges between 5 and 7: 5-2-7.
Example 3:
Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 5 Output: 0 Explanation: The distance between a node and itself is 0.
Constraints:
- The number of nodes in the tree is in the range
[1, 104]. 0 <= Node.val <= 109- All
Node.valare unique. pandqare values in the tree.
struct Solution;
use rustgym_util::*;
use std::collections::HashMap;
use std::collections::HashSet;
trait Preorder {
fn preorder(&self, prev: i32, adj: &mut HashMap<i32, HashSet<i32>>);
}
impl Preorder for TreeLink {
fn preorder(&self, prev: i32, adj: &mut HashMap<i32, HashSet<i32>>) {
if let Some(node) = self {
let node = node.borrow();
let val = node.val;
if prev != -1 {
adj.entry(prev).or_default().insert(val);
adj.entry(val).or_default().insert(prev);
}
node.left.preorder(val, adj);
node.right.preorder(val, adj);
}
}
}
impl Solution {
fn find_distance(root: TreeLink, p: i32, q: i32) -> i32 {
let mut adj: HashMap<i32, HashSet<i32>> = HashMap::new();
root.preorder(-1, &mut adj);
Self::dfs(p, -1, &adj, q)
}
fn dfs(cur: i32, prev: i32, adj: &HashMap<i32, HashSet<i32>>, q: i32) -> i32 {
if cur == q {
0
} else {
for &next in adj[&cur].iter() {
if next != prev {
let dist = Self::dfs(next, cur, adj, q);
if dist != -1 {
return dist + 1;
}
}
}
-1
}
}
}
#[test]
fn test() {
let root = tree!(
3,
tree!(5, tree!(6), tree!(2, tree!(7), tree!(4))),
tree!(1, tree!(0), tree!(8))
);
let p = 5;
let q = 0;
let res = 3;
assert_eq!(Solution::find_distance(root, p, q), res);
let root = tree!(
3,
tree!(5, tree!(6), tree!(2, tree!(7), tree!(4))),
tree!(1, tree!(0), tree!(8))
);
let p = 5;
let q = 7;
let res = 2;
assert_eq!(Solution::find_distance(root, p, q), res);
let root = tree!(
3,
tree!(5, tree!(6), tree!(2, tree!(7), tree!(4))),
tree!(1, tree!(0), tree!(8))
);
let p = 5;
let q = 5;
let res = 0;
assert_eq!(Solution::find_distance(root, p, q), res);
}