Depth First order on tree - Node.js Data Structure

Node.js examples for Data Structure:Tree

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Description

Depth First order on tree

Demo Code


/**// w w  w  .j  a v  a2s.co m
  *
  * Implement a `DFSelect` method on this Tree class.
  *
  * DFSelect accepts a filter function, calls that function on each of the nodes
  * in Depth First order, and returns a flat array of node values of the tree
  * for which the filter returns true.
  *
  * Example:
  *   var root1 = new Tree(1);
  *   var branch2 = root1.addChild(2);
  *   var branch3 = root1.addChild(3);
  *   var leaf4 = branch2.addChild(4);
  *   var leaf5 = branch2.addChild(5);
  *   var leaf6 = branch3.addChild(6);
  *   var leaf7 = branch3.addChild(7);
  *   root1.DFSelect(function (value, depth) {
  *     return value % 2;
  *   })
  *   // [1, 5, 3, 7]
  *
  *   root1.DFSelect(function (value, depth) {
  *     return depth === 1;
  *   })
  *   // [2, 3]
  *
  */

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

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

Tree.prototype.DFSelect = function(filter) {
  var result = [];
  var depth = 0;
  
  var findChild = function(tree, depth) {
    if (filter(tree.value, depth)) {
      result.push(tree.value)
    }
    if (tree.children.length > 0) {
      for (var i = 0; i < tree.children.length; i++) {
        findChild(tree.children[i], depth + 1);
      }
    }
  }
  findChild(this, depth);
  return result;
};



/**
  * 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 root1 = new Tree(1);
var branch2 = root1.addChild(2);
var branch3 = root1.addChild(3);
var leaf4 = branch2.addChild(4);
var leaf5 = branch2.addChild(5);
var leaf6 = branch3.addChild(6);
var leaf7 = branch3.addChild(7);
console.log(root1.DFSelect(function (value, depth) {
 return value % 2;
}))
// [1, 5, 3, 7]

console.log(root1.DFSelect(function (value, depth) {
 return depth === 1;
}))
// [2, 3]

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