652. 寻找重复的子树

给定一棵二叉树
写成一坨屎了

睡觉啦

class Solution {
    HashSet<String> set =new HashSet<>();
    List<TreeNode> lists = new ArrayList<>();
    List<String> help = new ArrayList<>();
    HashSet<String> set1= new HashSet<>();
    HashMap<String,TreeNode> map1 = new HashMap<>();
    HashMap<TreeNode,String> map2 = new HashMap<>();
    public List<TreeNode> findDuplicateSubtrees(TreeNode root) {
     // 给定一棵二叉树root  返回所有重复的子树
           dfs1(root);
            dfs(root);
            for(String str: help){
                lists.add(map1.get(str));
            }
             return lists;
    } 
    public String dfs1(TreeNode root){
        StringBuilder sb =new StringBuilder();
        if(root == null){
            return "null";
        }
        sb.append(root.val);
        sb.append("(");
        sb.append(dfs1(root.left));
        sb.append(")");
        sb.append("(");
        sb.append(dfs1(root.right));
        sb.append(")");
        map2.put(root,sb.toString());
        map1.put(sb.toString(),root);
        return sb.toString();
    }
     public void dfs(TreeNode root){
         if(root == null){
             return;
         }
          String temp = map2.get(root);
          if(set.contains(temp)){
              if(!set1.contains(temp)){
               help.add(temp);
              }
              set1.add(temp);
          }
          set.add(temp);
          dfs(root.left);
          dfs(root.right);
          
     }
}

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