adventofcode-2021/day15/part1.lua
Felix Van der Jeugt 9cdcdc1208
day 15
2021-12-15 10:51:53 +01:00

48 lines
1.0 KiB
Lua
Executable File

#!/usr/bin/env luajit
require("utils")
require("pqueue")
local grid = {}
for line in io.lines(arg[3]) do
local row = {}
for char in chars(line) do
table.insert(row, tonumber(char))
end
table.insert(grid, row)
end
function printgrid()
for r, row in pairs(grid) do
for c, cell in pairs(row) do
io.write(string.format("%3d", cell))
end
io.write('\n')
end
end
local pq = pqueue(function(a, b)
return a[3] < b[3]
end)
local distances = {}
local H = math.huge
local n = { 1, 1, 0 }
while n ~= nil and (distances[#grid] == nil or distances[#grid][#grid[1]] == nil) do
local r, c, d = unpack(n)
if 0 < r or r <= #grid or 0 < c or c <= #grid[r] then
local row = distances[r] or {}
if d < (row[c] or H) then
row[c] = d
distances[r] = row
pq:add({ r-1, c, d + ((grid[r-1] or {})[c] or H) })
pq:add({ r, c-1, d + ((grid[r] or {})[c-1] or H) })
pq:add({ r+1, c, d + ((grid[r+1] or {})[c] or H) })
pq:add({ r, c+1, d + ((grid[r] or {})[c+1] or H) })
end
end
n = pq:pop()
end
print(distances[#grid] and distances[#grid][#grid[1]])