剑指Offer(第二版)：59 - I. 滑动窗口的最大值 37. 序列化二叉树

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class Solution {
    public int[] maxSlidingWindow(int[] nums, int k) {
        //边界判断，可以不写，因为已经给了范围
        if(nums.length==0 || k>nums.length)
            return new int[0];
        //返回数组
        int[] res = new int[nums.length-k+1];
        //创建队列   队列的要求：1、首先存放的是下标  2、队列中存放的下标对应的值是递减的
        linkedList queue = new linkedList<>();
        //每次移动右指针
        for(int rIdx = 0 ; rIdx=nums[queue.peekLast()]){
                queue.removeLast();
            }
            queue.addLast(rIdx);
            //求窗口左侧边界
            int lIdx = rIdx-k+1;
            //判断2 这是判断窗口长度的
            if(queue.peekFirst()=k)
                res[lIdx] = nums[queue.peekFirst()]; 
        }
        return res;
    }
}

public class Codec {

    // Encodes a tree to a single string. 
    public String serialize(TreeNode root) {

        if(root == null) return "[]";
        StringBuilder res = new StringBuilder("[");

        //①：bfs
        Queue queue = new linkedList<>() {{ add(root); }};
        while(!queue.isEmpty()) {
            TreeNode node = queue.poll();
            if(node != null) {
                res.append(node.val + ",");
                queue.add(node.left);
                queue.add(node.right);
            }
            else res.append("null,");
        }
        //②：dfs怎么写呢？  dfs(root ,res);   想错了，我们要和反序列化取反，都要bfs，或者都dfs
        
        
        res.deleteCharAt(res.length()-1);  //去除最后的","号。
        res.append("]");
        return res.toString();
    }
    // private void dfs(TreeNode node , StringBuilder res){
    //     if(node == null){
    //         res.append("null,");
    //         return;
    //     }
    //     res.append(node.val).append(",");
    //     dfs(node.left,res);
    //     dfs(node.right,res);
    // }
    



    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        //边界判断
        if(data.equals("[]"))
            return null;
        //找出所有的数
        String[] data_arr = data.substring(1,data.length()-1).split(",");
        TreeNode root = new TreeNode(Integer.parseInt(data_arr[0]));  //首节点
        //放入队列中
        Queue queue = new linkedList<>(){{add(root);}};
        //这时候数组下标  
        int i=1;
        while(!queue.isEmpty()){
            TreeNode node = queue.poll();
            if(!data_arr[i].equals("null")){
                node.left = new TreeNode(Integer.parseInt(data_arr[i]));
                queue.offer(node.left);
            }
            i++;
            if(!data_arr[i].equals("null")){
                node.right = new TreeNode(Integer.parseInt(data_arr[i]));
                queue.offer(node.right);
            }
            i++;
        }
        return root;
    }
}

// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.deserialize(codec.serialize(root));