day 2 puzzle 2

progress.yaml

@@ -1,4 +1,4 @@
 1:
   stars: 2
 2:
-  stars: 1
+  stars: 2

src/day2/puzzle2.typ

@@ -0,0 +1,98 @@
+#import "/src/utils.typ": *
+
+#let is-safe(levels) = {
+  let increasing
+  let safe = true
+  for i in range(levels.len() - 1) {
+    let d = levels.at(i + 1) - levels.at(i)
+    let abs-d = calc.abs(d)
+    if abs-d < 1 or abs-d > 3 {
+      safe = false
+      break
+    }
+    if i == 0 {
+      increasing = d > 0
+    } else if (d > 0) != increasing {
+      safe = false
+      break
+    }
+  }
+  return safe
+}
+
+#let solve-bruteforce(input) = {
+  let safe-cnt = 0
+  for line in input.split("\n") {
+    let nums = line.split(" ").map(n => int(n))
+    if is-safe(nums) {
+      safe-cnt += 1
+    } else {
+      for i in range(nums.len()) {
+        if is-safe(nums.slice(0, i) + nums.slice(i+1)) {
+          safe-cnt += 1
+          break
+        }
+      }
+    }
+  }
+  return safe-cnt
+}
+
+#let visualize(input) = {
+  let safe-cnt = 0
+  for line in input.split("\n") {
+    let nums = line.split(" ").map(n => int(n))
+
+    let remove-i = none
+    if not is-safe(nums) {
+      for i in range(nums.len()) {
+        if is-safe(nums.slice(0, i) + nums.slice(i+1)) {
+          remove-i = i
+          break
+        }
+      }
+    }
+
+    let cells = ()
+    cells += nums.enumerate().map(((i, n)) => grid.cell(
+      colspan: 3,
+      fill: if i == remove-i {gray.transparentize(40%)},
+      str(n)
+    ))
+    cells += (none,none,)
+    cells += range(nums.len() - 1).map(i => nums.at(i + 1) - nums.at(i))
+                                  .map(n => {
+                                    let col = if calc.abs(n) in (1,2,3) {green} else {red}
+                                    grid.cell(
+                                      colspan: 2,
+                                      fill: gradient.linear(
+                                        angle: if n >= 0 {0deg} else {180deg},
+                                        (white, 0%),
+                                        (white, 50%),
+                                        (col, 50%),
+                                        (col, 100%)
+                                      ),
+                                      str(n)
+                                    )
+                                  })
+                                  .intersperse(none)
+
+    grid(
+      columns: (1fr,) * 3 * nums.len(),
+      inset: (x: 0.2em, y: 0.4em),
+      stroke: (x, y) => {
+        if y == 0 or (calc.rem(x, 3) == 2 and x != nums.len() * 3 - 1) {
+          black + .5pt
+        }
+      },
+      ..cells
+    )
+  }
+}
+
+#show-puzzle(
+  2, 2,
+  solve-bruteforce,
+  example: 4,
+  visualize: visualize
+)