100. Same Tree

/**
 * 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 {
    List<Integer> list1 = new ArrayList<>();
    List<Integer> list2 = new ArrayList<>();

    public boolean isSameTree(TreeNode p, TreeNode q) {
        treeOne(p);
        treeTwo(q);
        return list1.equals(list2);
    }

    void treeOne(TreeNode p) {
        if (p == null) {
            list1.add(null);
            return;
        }

        list1.add(p.val);
        treeOne(p.left);
        treeOne(p.right);
    }

    void treeTwo(TreeNode q) {
        if (q == null) {
            list2.add(null);
            return;
        }

        list2.add(q.val);
        treeTwo(q.left);
        treeTwo(q.right);
    }
}