Solution.java

/**
 * 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 {
    private List<Integer> seen;

    public boolean checkEqualTree(TreeNode root) {
        seen = new ArrayList<>();
        int s = sum(root);
        if (s % 2 != 0) {
            return false;
        }
        seen.remove(seen.size() - 1);
        return seen.contains(s / 2);
    }

    private int sum(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int l = sum(root.left);
        int r = sum(root.right);
        int s = l + r + root.val;
        seen.add(s);
        return s;
    }
}