872. Leaf-Similar Trees

Question:

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.

Note:

  • Both of the given trees will have between 1 and 100 nodes.

Solution:

  • Method 1: dfs ```Java /**
    • Definition for a binary tree node.
    • public class TreeNode {
    • int val;
    • TreeNode left;
    • TreeNode right;
    • TreeNode(int x) { val = x; }
    • } */ class Solution { private List leaves1; private List leaves2; public boolean leafSimilar(TreeNode root1, TreeNode root2) { this.leaves1 = new ArrayList<>(); this.leaves2 = new ArrayList<>(); dfs(root1, leaves1); dfs(root2, leaves2); if(leaves1.size() != leaves2.size()) return false; for(int i = 0; i < leaves1.size(); i++){ if(leaves1.get(i) != leaves2.get(i)) return false; } return true; } private void dfs(TreeNode node, List list){ if(node.left == null && node.right == null){ list.add(node.val); return; } if(node.left != null) dfs(node.left, list); if(node.right != null) dfs(node.right, list); } } ```