力扣——单值二叉树

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean isUnivalTree(TreeNode root) {
        boolean left_correct = (root.left == null ||
                (root.val == root.left.val && isUnivalTree(root.left)));
        boolean right_correct = (root.right == null ||
                (root.val == root.right.val && isUnivalTree(root.right)));
        return left_correct && right_correct;
    }
}