# 872. Leaf-Similar Trees

## Description

Consider all the leaves of a binary tree, from left to right order, the values of those leaves form a leaf value sequence.

For example, in the given tree above, the leaf value sequence is (6, 7, 4, 9, 8).

Two binary trees are considered leaf-similar if their leaf value sequence is the same.

Return true if and only if the two given trees with head nodes root1 and root2 are leaf-similar.

Example 1:

Input: root1 = [3,5,1,6,2,9,8,null,null,7,4], root2 = [3,5,1,6,7,4,2,null,null,null,null,null,null,9,8]
Output: true


Example 2:

Input: root1 = [1,2,3], root2 = [1,3,2]
Output: false


Constraints:

• The number of nodes in each tree will be in the range [1, 200].
• Both of the given trees will have values in the range [0, 200].

## Solutions

• /**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode() {}
*     TreeNode(int val) { this.val = val; }
*     TreeNode(int val, TreeNode left, TreeNode right) {
*         this.val = val;
*         this.left = left;
*         this.right = right;
*     }
* }
*/
class Solution {
public boolean leafSimilar(TreeNode root1, TreeNode root2) {
List<Integer> l1 = dfs(root1);
List<Integer> l2 = dfs(root2);
return l1.equals(l2);
}

private List<Integer> dfs(TreeNode root) {
if (root == null) {
return new ArrayList<>();
}
List<Integer> ans = dfs(root.left);
if (ans.isEmpty()) {
}
return ans;
}
}

• /**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode() : val(0), left(nullptr), right(nullptr) {}
*     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
*     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
bool leafSimilar(TreeNode* root1, TreeNode* root2) {
return dfs(root1) == dfs(root2);
}

vector<int> dfs(TreeNode* root) {
if (!root) return {};
auto ans = dfs(root->left);
auto right = dfs(root->right);
ans.insert(ans.end(), right.begin(), right.end());
if (ans.empty()) ans.push_back(root->val);
return ans;
}
};

• # Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
def leafSimilar(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> bool:
def dfs(root):
if root is None:
return []
ans = dfs(root.left) + dfs(root.right)
return ans or [root.val]

return dfs(root1) == dfs(root2)


• /**
* Definition for a binary tree node.
* type TreeNode struct {
*     Val int
*     Left *TreeNode
*     Right *TreeNode
* }
*/
func leafSimilar(root1 *TreeNode, root2 *TreeNode) bool {
var dfs func(*TreeNode) []int
dfs = func(root *TreeNode) []int {
if root == nil {
return []int{}
}
ans := dfs(root.Left)
ans = append(ans, dfs(root.Right)...)
if len(ans) == 0 {
ans = append(ans, root.Val)
}
return ans
}
return reflect.DeepEqual(dfs(root1), dfs(root2))
}

• // Definition for a binary tree node.
// #[derive(Debug, PartialEq, Eq)]
// pub struct TreeNode {
//   pub val: i32,
//   pub left: Option<Rc<RefCell<TreeNode>>>,
//   pub right: Option<Rc<RefCell<TreeNode>>>,
// }
//
// impl TreeNode {
//   #[inline]
//   pub fn new(val: i32) -> Self {
//     TreeNode {
//       val,
//       left: None,
//       right: None
//     }
//   }
// }
use std::rc::Rc;
use std::cell::RefCell;
impl Solution {
pub fn leaf_similar(
root1: Option<Rc<RefCell<TreeNode>>>,
root2: Option<Rc<RefCell<TreeNode>>>
) -> bool {
let mut one_vec: Vec<i32> = Vec::new();
let mut two_vec: Vec<i32> = Vec::new();

// Initialize the two vector
Self::traverse(&mut one_vec, root1);
Self::traverse(&mut two_vec, root2);

one_vec == two_vec
}

fn traverse(v: &mut Vec<i32>, root: Option<Rc<RefCell<TreeNode>>>) {
if root.is_none() {
return;
}
if Self::is_leaf_node(&root) {
v.push(root.as_ref().unwrap().borrow().val);
}
let left = root.as_ref().unwrap().borrow().left.clone();
let right = root.as_ref().unwrap().borrow().right.clone();
Self::traverse(v, left);
Self::traverse(v, right);
}

fn is_leaf_node(node: &Option<Rc<RefCell<TreeNode>>>) -> bool {
node.as_ref().unwrap().borrow().left.is_none() &&
node.as_ref().unwrap().borrow().right.is_none()
}
}


• var leafSimilar = function (root1, root2) {
const dfs = root => {
if (!root) {
return [];
}
let ans = [...dfs(root.left), ...dfs(root.right)];
if (!ans.length) {
ans = [root.val];
}
return ans;
};
const l1 = dfs(root1);
const l2 = dfs(root2);
return l1.toString() === l2.toString();
};