private static void Dfs(LeetCode938Node root, int L, int R)
{
if (root == null)
{
return;
}
if (root.val >= L && root.val <= R)
{
ans += root.val;
}
if (root.val > L)
{
Dfs(root.left, L, R);
}
if (root.val < R)
{
Dfs(root.right, L, R);
}
}
public LeetCode938Node(int val = 0, LeetCode938Node left = null, LeetCode938Node right = null)
{
this.val = val;
this.left = left;
this.right = right;
}
public static int RangeSumBST(LeetCode938Node root, int L, int R)
{
ans = 0;
Dfs(root, L, R);
return(ans);
}
