class Solution {
    int res,k;
    //注意kthLargest方法要放在dfs方法前，因为涉及到k的赋值
    public int kthLargest(TreeNode root, int k) {
        this.k = k;
        dfs(root);
        return res;
    }
    public void dfs(TreeNode root) {
        if(root == null) {
            return;
        }
        dfs(root.right);
        if(k == 0) {
            return;
        }
        if(--k == 0) {
           res = root.val;
        }
        dfs(root.left);
    }
}