aoc2021_day25_part1.js

(function(inp)
{
    const EMPTY = '.';
    const EAST = '>';
    const SOUTH = 'v';
    function Space(occupier)
    {
        this.nextEast = null;
        this.nextSouth = null;
        this.occupier = occupier;
        this.moveable = false;
    }
    
    Space.prototype.addSouthSpace = function(space)
    {
        if(this.nextSouth == null)
        {
            this.nextSouth = space;
        }
        else
        {
            this.nextSouth.addSouthSpace(space);
        }
    }
    
    Space.prototype.isEmpty = function()
    {
        return this.occupier == EMPTY;
    }
    
    Space.prototype.setMoveable = function(direction)
    {        
        this.moveable = false;
        
        if(this.occupier == direction)
        {
            if(direction == EAST)
            {
                this.moveable = this.nextEast.isEmpty();
            }
            else if(direction == SOUTH)
            {
                this.moveable = this.nextSouth.isEmpty();
            }
        }
        return this.moveable;
    }
    
    Space.prototype.move = function(direction)
    {
        if(this.occupier == direction && this.moveable)
        {
            if(this.occupier == EAST)
            {
                this.nextEast.occupier = EAST;
                this.occupier = EMPTY;
            }
            else if(this.occupier = SOUTH)
            {
                this.nextSouth.occupier = SOUTH;
                this.occupier = EMPTY;
            }
        }
    }
    
    function draw(firstSpace)
    {
        let finalString = '';
        let leftEdge = firstSpace;
        let done = false;
        
        while(!done)
        {
          finalString += leftEdge.occupier;
          let nextSpace = leftEdge.nextEast;
          while(nextSpace != leftEdge)
          {
              finalString += nextSpace.occupier;
              nextSpace = nextSpace.nextEast;
          }
           
          if(nextSpace == leftEdge)
          {
              finalString += '\n';
              leftEdge = leftEdge.nextSouth;
              done = leftEdge == firstSpace;
          }
        }
        
        return finalString;
    }
    
    function setMoveable(firstSpace, direction)
    {
        let done = false;
        let leftEdge = firstSpace;
        let movementOccurred = false;
        while(!done)
        {
          movementOccurred = leftEdge.setMoveable(direction) || movementOccurred;
          let nextSpace = leftEdge.nextEast;
          while(nextSpace != leftEdge)
          {
              movementOccurred = nextSpace.setMoveable(direction) || movementOccurred;
              nextSpace = nextSpace.nextEast;
          }
           
          if(nextSpace == leftEdge)
          {
              leftEdge = leftEdge.nextSouth;
              done = leftEdge == firstSpace;
          }
        }
        return movementOccurred;
    }
    
    function move(firstSpace, direction)
    {
        let done = false;
        let leftEdge = firstSpace;
        while(!done)
        {
          leftEdge.move(direction);
          let nextSpace = leftEdge.nextEast;
          while(nextSpace != leftEdge)
          {
              nextSpace.move(direction);
              nextSpace = nextSpace.nextEast;
          }
           
          if(nextSpace == leftEdge)
          {
              leftEdge = leftEdge.nextSouth;
              done = leftEdge == firstSpace;
          }
        }
    }
    
    let lines = inp.split('\n');
    let height = lines.length;
    let width = lines[0].length;
    
    let topSpaces = [];
    let firstSpace = null;
    let lastTop = null;
    let lastLeft = null;
    
    for(let li = 0; li < lines.length; li++)
    {
        let line = lines[li];
        let leftSpaces = [];
        for(let ci = 0; ci < line.length; ci++)
        {
            let c = line[ci];
            let sp = new Space(c);
 
            if(ci == 0 && li == 0)
            {
                firstSpace = sp;
            }    

            if(leftSpaces.length > 0)
            {
                leftSpaces[leftSpaces.length-1].nextEast = sp;
            }
            leftSpaces.push(sp);            
            if(li == 0)
            {
                topSpaces.push(sp);
            }
            else
            {
                topSpaces[ci].addSouthSpace(sp);
            }
        }
        leftSpaces[leftSpaces.length-1].nextEast = leftSpaces[0];
    }
    for(let sp of topSpaces)
    {
        sp.addSouthSpace(sp);
    }
    let movementOccured = setMoveable(firstSpace, EAST);
    move(firstSpace, EAST);
    movementOccured = setMoveable(firstSpace, SOUTH) || movementOccured;
    move(firstSpace, SOUTH);
    let moves = 1;
    while(movementOccured)
    {
        movementOccured = setMoveable(firstSpace, EAST);
        move(firstSpace, EAST);        
        movementOccured = setMoveable(firstSpace, SOUTH) || movementOccured;
        move(firstSpace, SOUTH);
        moves++;
    }
    return moves;
})(document.querySelector('pre').innerText.trim());