Java - tree data structure with multiple nodes - how to search efficiently

j2emanue :

I am searching for a implementation/data structure for some categories and child categories that i have. I am thinking to use a search tree but not sure how to begin implementation.

Let me show you what the data looks like. its acutally coming to me as a json structure from back end but it looks like this:

  [
    {
      "id": 94,
      "category_name": "New In", //this is the category category_name
      "description": "",
      "children": [ //this is the category children which can also be a sub-category
        {
          "id": 322,
          "category_name": "New Studio",
          "description": "Chic, sophisticated and polished with a classic edge."
        },
        {
          "id": 365,
          "category_name": "New Soho",
          "description": "Fresh, eclectic, and trendy. Oozes effortless cool."
        },
        {
          "id": 809,
          "category_name": "Summer Collection",
          "description": "Your ultimate summer look"
        }
      ]
    },
    {
      "id": 12,
      "category_name": "Clothes",
      "description": "",
      "children": [
        {
          "id": 22,
          "category_name": "All Clothes",
          "description": ""
        },
        {
          "id": 63,
          "category_name": "Tops",
          "description": "",
          "children": [
            {
              "id": 5,
              "category_name": "All Tops",
              "description": ""
            }

          ]
        },
        {
          "id": 641,
          "category_name": "Accessories",
          "description": "",
          "children": [
            {
              "id": 61,
              "category_name": "All Accessories",
              "description": ""
            },
            {
              "id": 622,
              "category_name": "Jewelry",
              "description": "",
              "children": [ // here is an example of a child that is a sub-category also
                {
                  "id": 52,
                  "category_name": "All Jewelry",
                  "description": ""
                },
                {
                  "id": 68,
                  "name": "Necklaces",
                  "description": ""
                },
                {
                  "id": 69,
                  "name": "Bracelets",
                  "description": ""
                },

              ]
            },

  ]

so if i had to draw this out it would look something like this:

So i want to be able to get path to anything. So for example if i want to search for Necklaces, then i want as well as getting a necklace to get the path of : Categories/Accessories/Jewelry/Necklaces

Is there a built in data structure for this ? i am coding in java. I suppose i also need the nodes sorted in some kind of order maybe A-Z.

so far i have this:

class Node{
 String label;
 List<Node> children;
}

but then how to search ? and is there a better data structure ? I do not want to iterate over all the nodes during a search, is there a way to sort the tree so i dont have to do that ? How i have it now i'd have to iterate over all the children. is there a way to maybe sort alphaetically perhaps or some kind of sort that would make the lookup faster ?

Brian Risk :

You need two things for this:

In your Node object, have a reference to the parent node as well:

class Node{
    String label;
    List<Node> children;
    Node parent;
}

Create a HashMap that maps labels to the nodes:

HashMap<String, Node> labelsToNodes;

Then searching is done with the get() method in the HashMap. You get your category list by repeatedly getting the parent nodes. Let me know if you'd like the code for this and I'll add it (I'm short on time right now).