private static LeetCode105TreeNode Helper(int left, int right)
{
if (left == right)
{
return(null);
}
var root_val = preOrder[pre_idx];
var root = new LeetCode105TreeNode(root_val);
var index = idx_map[root_val];
pre_idx++;
root.left = Helper(left, index);
root.right = Helper(index + 1, right);
return(root);
}
public LeetCode105TreeNode(int val = 0, LeetCode105TreeNode left = null, LeetCode105TreeNode right = null)
{
this.val = val;
this.left = left;
this.right = right;
}