public static IList <IList <int> > LevelOrderBottom(LeetCode107TreeNode root)
{
Helper(root, 0);
var ans = new List <IList <int> >();
var stack = new Stack <IList <int> >();
foreach (var item in levels)
{
stack.Push(item);
}
while (stack.Count != 0)
{
ans.Add(stack.Pop());
}
return(ans);
}
private static void Helper(LeetCode107TreeNode root, int level)
{
if (root == null)
{
return;
}
if (levels.Count == level)
{
levels.Add(new List <int>());
}
levels[level].Add(root.val);
if (root.left != null)
{
Helper(root.left, level + 1);
}
if (root.right != null)
{
Helper(root.right, level + 1);
}
}
public LeetCode107TreeNode(int val = 0, LeetCode107TreeNode left = null, LeetCode107TreeNode right = null)
{
this.val = val;
this.left = left;
this.right = right;
}