day 7 puzzle 2

progress.yaml

@@ -11,4 +11,4 @@
 6:
   stars: 1
 7:
-  stars: 1
+  stars: 2

src/day7/puzzle2.typ

@@ -0,0 +1,60 @@
+#import "/src/utils.typ": *
+
+#let concat(a, b) = {
+  return int(str(a) + str(b))
+}
+
+#let solveable(values, target) = {
+  if values.len() == 1 {
+    return values.last() == target
+  }
+
+  let values = values
+  let v = values.pop()
+  if calc.rem(target, v) == 0 {
+    if solveable(values, target / v) {
+      return true
+    }
+  }
+  let str-target = str(target)
+  let str-v = str(v)
+  if str-target == str-v {
+    return false
+  }
+  if str-target.ends-with(str-v) {
+    let target2 = str-target.slice(
+      0,
+      str-target.len() - str-v.len()
+    )
+    if solveable(values, int(target2)) {
+      return true
+    }
+  }
+  if v > target {
+    return false
+  }
+
+  return solveable(values, target - v)
+}
+
+#let solve(input) = {
+  let equations = input.split("\n")
+
+  let total = 0
+  for equation in equations {
+    let (target, values) = equation.split(": ")
+    target = int(target)
+    values = values.split(" ").map(int)
+
+    if solveable(values, target) {
+      total += target
+    }
+  }
+  return total
+}
+
+#show-puzzle(
+  7, 2,
+  solve,
+  example: 11387
+)