private static void Helper(LeetCode144TreeNode root) { if (root == null) { return; } ans.Add(root.val); Helper(root.left); Helper(root.right); }
public static IList <int> PreorderTraversal(LeetCode144TreeNode root) { Helper(root); return(ans); }
public LeetCode144TreeNode(int val = 0, LeetCode144TreeNode left = null, LeetCode144TreeNode right = null) { this.val = val; this.left = left; this.right = right; }