advent of code 2021 day 15

psuedocode

# assuming positions are 2-tuple of row, column coordinates
def shortest_risk(cave, risk_total = 0, current_position)
  if is_exit(cave, current_position):
    return risk_total + cave[current_position]
  
  new_total = risk_total + cave[current_position]
  new_cave = mark_cave_visited(cave, current_position)

  left = [current_position[0], current_position[1] - 1]
  right = [current_position[0], current_position[1] + 1]
  up [current_position[0] - 1, current_position[1]]
  down = [current_position[0] + 1, current_position[1]]

  candidates = []

  if is_explorable(cave, left):
    candidates.push(shortest_risk(new_cave, new_total, left))

  if is_explorable(cave, right):
    candidates.push(shortest_risk(new_cave, new_total, right))

  if is_explorable(cave, up):
    candidates.push(shortest_risk(new_cave, new_total, up))

  if is_explorable(cave, down):
    candidates.push(shortest_risk(new_cave, new_total, down))

  if candidates.length == 0:
    return 9999999 # some high value, we are at a dead end so we want to rule this path out

  return min(candidates)

def is_explorable(cave, position): 
    return !already_visited(cave, position) and !out_of_bounds(cave, position)

def is_exit(cave, position):
  # implement this

def out_of_bounds(cave, position):  
  # implement this

def mark_cave_visited(cave, current_position):
  # return copy of cave but with the current_position set to some special value representing visited

def already_visited(cave, position):
  # does this position == the special "visited" value?