refactor day 2 considerably

02/index.ts

@@ -2,33 +2,31 @@ import fs from "node:fs";
 
 const data = fs.readFileSync("./inputs/input", "utf8");
 
-type runner = { ok: boolean; prev: number; inc: boolean; dec: boolean };
+type collector = { ok: boolean; inc: boolean; dec: boolean };
 
-const testFunc = (running: runner, current: number, i: number) => {
-  if (i === 0) {
-    return { ok: true, prev: current, inc: false, dec: false };
-  }
-  if (!running.ok) {
-    // quick exit
-    return running;
-  }
-  const diff = Math.abs(running.prev - current);
-  return {
-    ok: diff > 0 && diff < 4,
-    prev: current,
-    inc: running.inc || running.prev - current > 0,
-    dec: running.dec || running.prev - current < 0,
-  };
+const init = {
+  ok: true,
+  inc: false,
+  dec: false,
 };
 
+const reducer = (col: collector, curr: number, i: number, a: number[]) =>
+  i === 0 || !col.ok
+    ? col
+    : {
+        ok:
+          a[i - 1] - curr > -4 && a[i - 1] - curr !== 0 && a[i - 1] - curr < 4,
+        inc: col.inc || a[i - 1] - curr > 0,
+        dec: col.dec || a[i - 1] - curr < 0,
+      };
+
+const isOK = (r: collector): boolean => r.ok && !(r.inc && r.dec);
+
 const permute = (report: number[]): number[][] => {
-  const result: Array<Array<number>> = Array.from(
-    { length: report.length },
-    () => []
-  );
-  return result.map((_, i) => {
-    return [...report.slice(0, i), ...report.slice(i + 1)];
-  });
+  return Array.from({ length: report.length }, (_, i) => [
+    ...report.slice(0, i),
+    ...report.slice(i + 1),
+  ]);
 };
 
 console.log(
@@ -37,10 +35,11 @@ console.log(
     .split("\n")
     .slice(0, -1) // remove empty trailing newline
     .map((v) => v.split(" ").map((c) => parseInt(c, 10)))
-    .reduce((total, current) => {
-      const tmp = current.reduce(testFunc, {} as runner);
-      return (tmp.inc && tmp.dec) || !tmp.ok ? total : total + 1;
-    }, 0)
+    .reduce(
+      (total, current) =>
+        isOK(current.reduce(reducer, init)) ? total + 1 : total,
+      0
+    )
 );
 
 console.log(
@@ -49,18 +48,14 @@ console.log(
     .split("\n")
     .slice(0, -1) // remove empty trailing newline
     .map((v) => v.split(" ").map((c) => parseInt(c, 10)))
-    .reduce((total, current) => {
-      const tmp = current.reduce(testFunc, {} as runner);
-      // ok, that was fine.
-      if (tmp.ok && !(tmp.inc && tmp.dec)) {
-        return total + 1;
-      }
-      // otherwise, brute force!
-      const tmp2 = permute(current)
-        .map((v) => v.reduce(testFunc, {} as runner))
-        .reduce((coll, curr) => {
-          return coll || (curr.ok && !(curr.inc && curr.dec));
-        }, false);
-      return tmp2 ? total + 1 : total;
-    }, 0)
+    .reduce(
+      (total, current) =>
+        isOK(current.reduce(reducer, init)) ||
+        permute(current)
+          .map((v) => v.reduce(reducer, init))
+          .reduce((coll, curr) => coll || isOK(curr), false)
+          ? total + 1
+          : total,
+      0
+    )
 );