Breadth first traversal of object

Question

I am making a program that solves a puzzle game, and it finds all the possible moves on a board and puts all the possible resulting boards in an object. Then it finds all the possible moves for the resulting boards, and so on. The object will look something like this:

{
  "board": {
      "starts": [[0,0],[0,3]],
      "blocks": [[3,0],[3,3]],
      "ends":   [[2,4]]
  },
  "possibleMoves": [
    {
      "board": {
        "starts": [[0,0],[2,3]],
        "blocks": [[3,0],[3,3]],
        "ends":   [[2,4]]
      },
      "possibleMoves":[
        {
          "board": {},
          "possibleMoves": [{}]
        }
      ]
    },
    {
      "board": {
        "starts": [[0,3]],
        "blocks": [[3,0],[3,3]],
        "ends":   [[2,4]]
      },
      "possibleMoves":[{}]
    }]
}

I can figure out how to add the possible moves from the top-level board, but I cannot figure out how to loop through all the resulting boards in the second level and figure out their possible moves, and then loop through all the third level boards and so on. How can I add the possible moves and traverse the object using a breadth-first search?

Answer 1

Recursion.

function traverse(state) {
    handle(state.board);
    if (state.possibleMoves) {
        $.each(state.possibleMoves, function(i, possibleMove) {
             traverse(possibleMove);
        });
    }
}

EDIT: For a breadth-first search, try something like this. It doesn't use recursion, but instead iterates over a growing queue.

function traverse(state) {
    var queue = [],
        next = state;
    while (next) {
        if (next.possibleMoves) {
            $.each(next.possibleMoves, function(i, possibleMove) {
                queue.push(possibleMove);
            });
        }
        next = queue.shift();
    }
}

Answer 2

Not completely tested:

var oo = {
    board: {
        starts: [[0,0],[0,3]],
        blocks: [[3,0],[3,3]],
        ends:   [[2,4]]
    },
    possibleMoves: [{
        board: {
            starts: [[0,0],[2,3]],
            blocks: [[3,0],[3,3]],
            ends:   [[2,4]]
        },
    }],
};


function traverseObject (o) {
    for (var prop in o) {
        if (typeof o[prop] == "array" || typeof o[prop] == "object") {
            traverseObject(o[prop]);
            console.log(prop);
        } else {
            console.log(prop, "=", o[prop]);
        }
    }
}

traverseObject(oo);

Answer 3

I don't have a JavaScript description but i would generally do it by keeping a queue of unexplored nodes.

1. Start with only the root node in the queue.
2. Pop an item from the front of the queue
3. Explore it add all of the nodes found during exploration to the back of the queue
4. Check if there are any nodes in the queue if there are go back to step 2
5. Your done

Also there is some pseudopod on the Wikipedia page as well as some more explanations HERE

Also a quick Google search turned up a similar algorithm that could be bent to your purpose HERE