559. N 叉树的最大深度

559. N 叉树的最大深度

     public int maxDepth(Node root) {
        if (root == null) {
      return 0;
    } else if (root.children.isEmpty()) {
      return 1;  
    } else {
      List<Integer> heights = new LinkedList<>();
      for (Node item : root.children) {
        heights.add(maxDepth(item)); 
      }
      return Collections.max(heights) + 1;
    }

    public int maxDepth(Node root) {
        Queue<Node> que=new LinkedList();
        int depth=0;
        if(root!=null){
            que.add(root);
        }
        while(!que.isEmpty()){
            int size=que.size();
            depth++;
            for(int i=0;i<size;i++){
                Node node=que.peek();
                que.poll();
                for(Node val:node.children){
                    if(val!=null){
                        que.add(val);
                    }
                }
            }
        }
        return depth;
    }

public int maxDepth(Node root) {
    Queue<Pair<Node, Integer>> stack = new LinkedList<>();
    if (root != null) {
      stack.add(new Pair(root, 1));
    }
    int depth = 0;
    while (!stack.isEmpty()) {
      Pair<Node, Integer> current = stack.poll();
      root = current.getKey();
      int current_depth = current.getValue();
      if (root != null) {
        depth = Math.max(depth, current_depth);
        for (Node c : root.children) {
          stack.add(new Pair(c, current_depth + 1));    
        }
      }
    }
    return depth;
  }
//作者：LeetCode
//链接：https://leetcode-cn.com/problems/maximum-depth-of-n-ary-tree/solution/ncha-shu-de-zui-da-shen-du-by-leetcode/

    public int maxDepth(Node root) {
        if (null == root) {
            return 0;
        }
        int result = 1;
        for (Node child : root.children) {
            result = Math.max(result, 1 + maxDepth(child));
        }
        return result;
    }