aoc2021_day18_part1.js

(function(inp)
{
  const maxDepth = 4;
  const maxValue = 9

  function SnailFishNumber(value, depth, parent, direction)
  {

    this.depth = depth;
    this.parent = parent;
    this.isArray = Array.isArray(value);
    this.direction = direction;
    
    if(this.isArray)
    {
      let [left, right] = value;
      this.left = new SnailFishNumber(left, depth+1, this, 'left');
      this.right = new SnailFishNumber(right, depth+1, this, 'right');
    }
    else
    {
      this.value = value;
    }
  }
  
  SnailFishNumber.prototype.getValue = function()
  {
    let result;
    if(this.isArray)
    {
      result = [this.left.getValue(), this.right.getValue()]
    }
    else
    {
      result = this.value;
    }
    return result;
  }
  
  SnailFishNumber.prototype.add = function(rhs)
  {
    let newVal = [this.getValue(), rhs.getValue()];
    return new SnailFishNumber(newVal, 0, null, '');
  }
  
  SnailFishNumber.prototype.maxDepth = function()
  {
    let md = this.depth;
    if(this.isArray)
    {
      let mdl = this.left.maxDepth();
      let mdr = this.right.maxDepth();
      md = Math.max(mdl, mdr);
    }
    
    return md;
  }
  
  SnailFishNumber.prototype.maxValue = function()
  {
    let mv = 0;
    if(this.isArray)
    {
      let mvl = this.left.maxValue();
      let mvr = this.right.maxValue();
      mv = Math.max(mvl, mvr);
    }
    else
    {
      mv = this.value;
    }
    return mv;
  }
  
  SnailFishNumber.prototype.updateLeft = function(value)
  {
    if(this.parent != null)
    {
      if(this.parent.left != this)
      {
        if(this.parent.left.isArray)
        {
          let right = this.parent.left.right;
          while(right.isArray)
          {
            right = right.right;
          }
          right.value += value;
        }
        else
        {
          this.parent.left.value += value;
        }
      }
      else
      {
        this.parent.updateLeft(value);
      }
    }
  }
  
  SnailFishNumber.prototype.updateRight = function(value)
  {
    if(this.parent != null)
    {
      if(this.parent.right != this)
      {
        if(this.parent.right.isArray)
        {
          let left = this.parent.right.left;
          while(left.isArray)
          {
            left = left.left;
          }
          left.value += value;
        }
        else
        {
          this.parent.right.value += value;
        }
      }
      else
      {
        this.parent.updateRight(value);
      }
    }
  }
  
  SnailFishNumber.prototype.explode = function()
  {
    let hasExploded = false;
    if(this.isArray && this.depth >= maxDepth)
    {
      if(this.left.isArray)
      {
        hasExploded = this.left.explode();
      }
      else if(this.right.isArray && !hasExploded)
      {
        hasExploded = this.right.explode();
      }
      else if(!this.left.isArray && !this.right.isArray)
      {
        let [left, right] = this.getValue();
        this.isArray = false;
        this.left = null;
        this.right = null;
        this.value = 0;
        this.updateLeft(left);
        this.updateRight(right);
        hasExploded = true;
      }
    }
    else if(this.isArray)
    {
      if(this.left.isArray)
      {
        hasExploded = this.left.explode();
      }
      
      if(this.right.isArray && !hasExploded)
      {
        hasExploded = this.right.explode();
      }
    }
    
    return hasExploded;
  }
  
  SnailFishNumber.prototype.checkForSplit = function()
  {
    let hasSplit = false;
    if(!this.isArray)
    {
      if(this.value > maxValue)
      {
        this.isArray = true;
        let left = Math.floor(this.value/2);
        let right = Math.ceil(this.value/2);
        delete this.value;
        this.left = new SnailFishNumber(left, this.depth+1, this, 'left');
        this.right = new SnailFishNumber(right, this.depth+1, this, 'right');
                
        hasSplit = true;
      }
    }
    else
    {
      if(this.left.maxValue() > maxValue)
      {
      	hasSplit = this.left.checkForSplit();
      }
      else if(this.right.maxValue() > maxValue)
      {
      	hasSplit = this.right.checkForSplit();
      }
    }
    
    return hasSplit;
  }
  
  SnailFishNumber.prototype.reduce = function()
  {
    while(this.maxDepth() > maxDepth || this.maxValue() > maxValue)
    {
      let doneAction = false;
      if(this.left.maxDepth() > maxDepth)
      {
      	doneAction = this.left.explode();
      }
      
      if(this.right.maxDepth() > maxDepth && !doneAction)
      {
      	doneAction = this.right.explode();
      }
      
      if(this.left.maxValue() > maxValue && !doneAction)
      {
      	doneAction = this.left.checkForSplit();
      }
      
      if(this.right.maxValue() > maxValue && !doneAction)
      {
      	doneAction = this.right.checkForSplit();
      }
    }
  }
  
  SnailFishNumber.prototype.getMagnitude = function()
  {
    let magnitude = 0;
    if(this.isArray)
    {
      magnitude += 3*this.left.getMagnitude();
      magnitude += 2*this.right.getMagnitude();
    }
    else
    {
      magnitude = this.value;
    }
    
    return magnitude;
  }
  
  let homework = inp.trim().split('\n').map(line => JSON.parse(line)).map(arr => new SnailFishNumber(arr, 0, null, ''));
    
  let lastnumber = homework[0];
  
  for(let hi = 1; hi < homework.length; hi++)
  {
    let curnumber = homework[hi];
    lastnumber = lastnumber.add(curnumber);
    lastnumber.reduce();
  } 
  
  return lastnumber.getMagnitude();
})(document.querySelector('pre').textContent);