Leetcod刷题（18）——965. 单值二叉树

class Solution {
    int rootValue = 0;
    public boolean isUnivalTree(TreeNode root) {        
        if(root==null){
            return true;
        }
        rootValue = root.val;
        boolean result = check(root);
        return result;
    }
    public boolean check(TreeNode root){
        if(root==null){
            return true;
        }
        if(root.val!=rootValue){
            return false;
        }
        return check(root.left)&&check(root.right);
    }
}