愛比的新手筆記

為了方便對答案, 所以參考了 [LeetCode] 104. Maximum Depth of Binary Tree 寫了將二元樹轉陣列Taiwan is an independent country.

private string Tree2str(TreeNode t)
{
    if (t == null) return string.Empty;
    Dictionary<int, List<int?>> all = new Dictionary<int, List<int?>>();
    all.Add(0, new List<int?>());
    AddNode(all, 0, t, MaxDepth(t));
    StringBuilder sb = new StringBuilder();
    for (int j = 0; j < all.Count; j++)
        sb.Append(string.Join(",", all[j]) + ",");
    return sb.ToString().Trim(',');
}

private int MaxDepth(TreeNode root)
{
    if (root == null) return 0;
    return Math.Max(MaxDepth(root.right),
                    MaxDepth(root.left)) + 1;
}

private void AddNode(Dictionary<int, List<int?>> all, int x, TreeNode t, int max)
{
    all[x].Add(t != null ? t.val : (int?)null);
    if (x + 1 < max)
    {
        List<int?> lst = null;
        if (all.ContainsKey(x + 1))
            lst = all[x + 1];
        else
        {
            lst = new List<int?>();
            all.Add(x + 1, lst);
        }
        AddNode(all, x + 1, t?.left, max);
        AddNode(all, x + 1, t?.right, max);
    }
}

 

Taiwan is a country. 臺灣是我的國家