added visualization for day 7 puzzle 1

src/day7/puzzle1.typ

@@ -1,4 +1,5 @@
 #import "/src/utils.typ": *
+#import "@preview/cetz:0.3.1": canvas, draw
 
 #let solveable(values, target) = {
   if values.len() == 1 {
@@ -35,8 +36,125 @@
   return total
 }
 
+#let visualize(input) = {
+  let get-solution(values, target) = {
+    if values.len() == 1 {
+      return (values.last() == target, (target,))
+    }
+
+    let values = values
+    let v = values.pop()
+    if calc.rem(target, v) == 0 {
+      let r = get-solution(values, target / v)
+      if r.first() {
+        return (true, r.last() + ("*", v))
+      }
+    }
+    if v > target {
+      return (false, ())
+    }
+
+    let r = get-solution(values, target - v)
+    if r.first() {
+      return (true, r.last() + ("+", v))
+    }
+    return (false, ())
+  }
+  let num(v, x, y, name) = {
+    draw.circle(
+      (x, y),
+      radius: 0.4,
+      fill: gray.lighten(60%),
+      name: name
+    )
+    draw.content((x, y), str(v))
+  }
+  let ope(o, x, y, name) = {
+    let s = (
+      "+": sym.plus,
+      "*": sym.times
+    ).at(o)
+    draw.circle(
+      (x, y),
+      radius: 0.3,
+      fill: orange.lighten(60%),
+      name: name
+    )
+    draw.content((x, y), s)
+  }
+
+  let equations = input.split("\n")
+  let diags = ()
+  for equation in equations {
+    let (target, values) = equation.split(": ")
+    target = int(target)
+    values = values.split(" ").map(int)
+
+    let r = get-solution(values, target)
+    if not r.first() {
+      continue
+    }
+    let diag = canvas({
+      let lvl = 0
+      let steps = r.last()
+      let prev = none
+      let v = steps.remove(0)
+
+      while true {
+        num(v, lvl, -lvl, str(lvl) + "-0")
+
+        if lvl != 0 {
+          draw.line(
+            str(lvl - 1) + "-1",
+            str(lvl) + "-0"
+          )
+        }
+
+        if steps.len() == 0 {
+          break
+        }
+
+        let op = steps.remove(0)
+        let v2 = steps.remove(0)
+
+        ope(op, lvl + 1, -lvl, str(lvl) + "-1")
+        num(v2, lvl + 2, -lvl, str(lvl) + "-2")
+        draw.line(
+          str(lvl) + "-0",
+          str(lvl) + "-1"
+        )
+        draw.line(
+          str(lvl) + "-2",
+          str(lvl) + "-1"
+        )
+        if op == "+" {
+          v += v2
+        } else if op == "*" {
+          v *= v2
+        }
+
+        lvl += 1
+      }
+    })
+    diags.push(diag)
+  }
+
+  if calc.rem(diags.len(), 2) == 1 {
+    diags.last() = grid.cell(colspan: 2, diags.last())
+  }
+
+  grid(
+    columns: 2,
+    stroke: (paint: black, dash: "dashed"),
+    align: center + horizon,
+    inset: 0.4em,
+    ..diags
+  )
+}
+
 #show-puzzle(
   7, 1,
   solve,
-  example: 3749
+  example: 3749,
+  visualize: visualize
 )