feat(day-1): add part 2 solution

Right to left match is not that simple huh?

1 files changed, 41 insertions, 4 deletions

diff --git a/day-1/script.ts b/day-1/script.ts
index 9e444ba..8398922 100644
--- a/day-1/script.ts
+++ b/day-1/script.ts
@@ -2,14 +2,51 @@ import fs from "fs";
 
 const input = fs.readFileSync("./input.txt").toString();
 
+const digits = [
+  "one",
+  "two",
+  "three",
+  "four",
+  "five",
+  "six",
+  "seven",
+  "eight",
+  "nine",
+];
+
+const re = new RegExp(`(${digits.join("|")}|\\d)`);
+const invertedRe = new RegExp(
+  `(${digits
+    .map((digit) => digit.split("").reverse().join(""))
+    .join("|")}|\\d)`,
+);
+
+function parseNumber(s: string) {
+  return s.length === 1
+    ? Number(s)
+    : digits.findIndex((digit) => digit === s) + 1;
+}
+
 const result = input
   .split("\n")
   .slice(0, -1)
-  .map((line) => line.match(/\d/g))
+  .map((line) => [
+    line.match(re)?.[0] || "",
+    // Reverse the string, find the inverted match right-to-left and reverse again
+    line
+      .split("")
+      .reverse()
+      .join("")
+      .match(invertedRe)?.[0]
+      .split("")
+      .reverse()
+      .join("") || "",
+  ])
   .reduce((acc, value) => {
-    if (!value)
-      throw new Error(`The string must contain at least one digit ${value}`);
-    return acc + Number(value[0] + value[value.length - 1]);
+    if (!value[0].length || !value[1].length) throw new Error("Match failed");
+    return (
+      acc + parseNumber(value[0]) * 10 + parseNumber(value[value.length - 1])
+    );
   }, 0);
 
 console.log({ result });