day 18 puzzle 1

src/day18/puzzle1.typ

@@ -0,0 +1,148 @@
+#import "/src/utils.typ": *
+
+#let offsets = (
+  (1, 0),
+  (0, 1),
+  (-1, 0),
+  (0, -1)
+)
+
+#let get-coords(x, y) = {
+  return str(x) + "/" + str(y)
+}
+
+#let get-lowest(nodes, scores) = {
+  let lowest-score = none
+  let lowest-i = none
+  for (i, (x, y)) in nodes.enumerate() {
+    let score = scores.at(y).at(x)
+
+    if lowest-i == none or score < lowest-score {
+      lowest-score = score
+      lowest-i = i
+    }
+  }
+
+  if lowest-i == none {
+    panic()
+  }
+  return lowest-i
+}
+
+#let make-path(parents, end) = {
+  let path = (end,)
+  let (x, y) = end
+  let pos = parents.at(y).at(x)
+  while pos != none {
+    (x, y) = pos
+    path.insert(0, pos)
+    pos = parents.at(y).at(x)
+  }
+  return path
+}
+
+#let find-path(w, h, grid, start: (0, 0), end: auto) = {
+  let end = if end == auto {(w - 1, h - 1)} else {end}
+  let end = (w - 1, h - 1)
+  let (x, y) = (0, 0)
+  let open = ((x, y),)
+  let closed = ()
+  let g-scores = ((0,) * w,) * h
+  let f-scores = ((calc.inf,) * w,) * h
+  let parents = ((none,)*w,)*h
+  while open.len() != 0 {
+    let cur = open.remove(get-lowest(open, f-scores))
+    
+    if cur == end {
+      return make-path(parents, cur)
+    }
+
+    let g-score = g-scores.at(y).at(x)
+    let f-score = f-scores.at(y).at(x)
+    
+    let (x, y) = cur
+    for (dx, dy) in offsets {
+      let (x2, y2) = (x + dx, y + dy)
+      if x2 < 0 or x2 >= w or y2 < 0 or y2 >= h {
+        continue
+      }
+      if grid.at(y2).at(x2) {
+        continue
+      }
+      if (x2, y2) in closed {
+        continue
+      }
+      let g = x2 + y2
+      let h = calc.abs(end.first() - x2) + calc.abs(end.last() - y2)
+      let f = g + h
+
+      if f < f-scores.at(y2).at(x2) {
+        g-scores.at(y2).at(x2) = g
+        f-scores.at(y2).at(x2) = f
+        parents.at(y2).at(x2) = (x, y)
+        open.push((x2, y2))
+      }
+    }
+    closed.push(cur)
+  }
+  panic("No path was found")
+}
+
+#let solve(input, w: 0, h: 0, n-bytes: 0) = {
+  assert(w != 0, message: "Width cannot be 0")
+  assert(h != 0, message: "Height cannot be 0")
+  let grid = ((false,) * w,) * h
+
+  let obstacles = input.split("\n")
+  for obs in obstacles.slice(0, n-bytes) {
+    let (x, y) = obs.split(",").map(int)
+    grid.at(y).at(x) = true
+  }
+
+  let path = find-path(w, h, grid)
+  return path.len() - 1
+}
+
+#let visualize(input, w: 0, h: 0, n-bytes: 0, s: 2em) = {
+  let grid_ = ((false,) * w,) * h
+
+  let obstacles = input.split("\n")
+  for obs in obstacles.slice(0, n-bytes) {
+    let (x, y) = obs.split(",").map(int)
+    grid_.at(y).at(x) = true
+  }
+
+  let path = find-path(w, h, grid_)
+  for (x, y) in path {
+    grid_.at(y).at(x) = grid.cell(fill: green.lighten(60%))[O]
+  }
+  
+  let cells = grid_.flatten().map(c => {
+    if c == false []
+    else if c == true {grid.cell(fill: red.lighten(60%))[\#]}
+    else {c}
+  })
+  
+  grid(
+    columns: (s,) * w,
+    rows: (s,) * h,
+    align: center + horizon,
+    stroke: black,
+    ..cells
+  )
+}
+
+#show-puzzle(
+  18, 1,
+  solve.with(w: 71, h: 71, n-bytes: 1024),
+  example: (
+    (result: 22, args: (w: 7, h: 7, n-bytes: 12)),
+  ),
+  visualize: visualize.with(w: 7, h: 7, n-bytes: 12)
+)
+
+/*
+#pagebreak()
+#set page(width: auto, height: auto)
+#visualize(get-input(18), w: 71, h: 71, n-bytes: 1024, s: 1em)
+*/