count Leaves function on Tree class - Node.js Data Structure

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Description

count Leaves function on Tree class

Demo Code


/**//from w  ww.j  a v  a2 s  .c om
  * Implement the `countLeaves` function in this Tree class.
  *
  * A leaf node is any node in the tree that has no children. `countLeaves` should
  * traverse the tree, and return the number of leaf nodes the tree contains.
  *
  * Illustration of a tree with three leaves:
  *
  *       * <- root
  *      / \
  *     *    * <- leaf
  *    / \
  *   *   * <- leaf
  *  /
  * * <- leaf
  *
  * Example usage:
  *   var root = new Tree();
  *   root.countLeaves(); // 1
  *   root.addChild(new Tree());
  *   root.countLeaves(); // still 1
  *   root.addChild(new Tree());
  *   root.children[0].addChild(new Tree());
  *   root.children[0].addChild(new Tree());
  *   root.children[0].children[0].addChild(new Tree());
  *   root.countLeaves(); // 3
  *
  */

/*
 * Basic tree that stores a value.
 */

var Tree = function(value) {
  this.value = value;
  this.children = [];
};

Tree.prototype.countLeaves = function () {
  // TODO: implement me!
  var count = 0;

  var findLeaf = function(tree) {
    if (tree.children.length > 0) {
      tree.children.forEach(function(element) {
        findLeaf(element);
      })
    } else {
      count++;
    }
  }
  findLeaf(this);
  return count;
};

/**
  * You shouldn't need to change anything below here, but feel free to look.
  */

/**
  * add an immediate child
  * (wrap values in Tree nodes if they're not already)
  */
Tree.prototype.addChild = function(child) {
  if (!child || !(child instanceof Tree)) {
    child = new Tree(child);
  }

  if (!this.isDescendant(child)) {
    this.children.push(child);
  } else {
    throw new Error('That child is already a child of this tree');
  }
  // return the new child node for convenience
  return child;
};

/**
  * check to see if the provided tree is already a child of this
  * tree __or any of its sub trees__
  */
Tree.prototype.isDescendant = function(child) {
  if (this.children.indexOf(child) !== -1) {
    // `child` is an immediate child of this tree
    return true;
  } else {
    for (var i = 0; i < this.children.length; i++) {
      if (this.children[i].isDescendant(child)) {
        // `child` is descendant of this tree
        return true;
      }
    }
    return false;
  }
};

/**
  * remove an immediate child
  */
Tree.prototype.removeChild = function(child) {
  var index = this.children.indexOf(child);
  if (index !== -1) {
    // remove the child
    this.children.splice(index, 1);
  } else {
    throw new Error('That node is not an immediate child of this tree');
  }
};

var root = new Tree();
root.countLeaves(); // 1
root.addChild(new Tree());
root.countLeaves(); // still 1
root.addChild(new Tree());
root.children[0].addChild(new Tree());
root.children[0].addChild(new Tree());
root.children[0].children[0].addChild(new Tree());
console.log(root.countLeaves()); // 3

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