day-3

day-3/index.js

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+import { testInput, testInput2 } from "./test.js";
+import { actualInput } from "./real.js";
+
+// testCode
+const input = testInput;
+// const input2 = testInput2;
+
+// Actual Input
+// const input = actualInput;
+const input2 = actualInput;
+
+// regex to get the mul() with 2 numbers of 1-3 digits each
+const mulRegexp = new RegExp(/(mul\()([0-9]{1,3},[0-9]{1,3})+(\))/, "g");
+// regex to get do()
+const doRegexp = new RegExp(/(do\(\))/, "g");
+// regex to get don't()
+const dontRegexp = new RegExp(/(don\'t\(\))/, "g");
+
+const getSumFromMul = (text) => {
+  const [a, b] = text.replace("mul(", "").replace(")", "").split(",");
+  const sum = a * b;
+  return sum;
+};
+
+const firstAnswer = () => {
+  const mulMatches = input.match(mulRegexp);
+
+  const answer = mulMatches.reduce((accumulator, currentValue) => {
+    // replace the mul() and split the numbers by the comma.
+    const sum = getSumFromMul(currentValue);
+    return accumulator + sum;
+  }, 0);
+  console.log("part-1 answer:", answer);
+};
+
+firstAnswer();
+
+const getPositions = (searchStr, regExp, type) => {
+  var regex = regExp,
+    result,
+    indices = [];
+  while ((result = regex.exec(searchStr))) {
+    indices.push({ index: result.index, type, result: result[0] });
+  }
+
+  return indices;
+};
+
+const secondAnswer = () => {
+  // mul is enabled at the start.
+  let enabled = true;
+
+  // search for locations of each string
+  const mulPositions = getPositions(input2, mulRegexp, "mul");
+  const doPositions = getPositions(input2, doRegexp, "do");
+  const dontPositions = getPositions(input2, dontRegexp, "dont");
+
+  // combine into one array, sorted by index.
+  const out = [...mulPositions, ...doPositions, ...dontPositions];
+  const flatOut = out.flat().sort((a, b) => a.index - b.index);
+
+  const ans = [];
+  flatOut.forEach((item) => {
+    if (enabled && item.type === "mul") {
+      // add to array
+      ans.push(item);
+    } else if (item.type === "do") {
+      enabled = true;
+    } else if (item.type === "dont") {
+      enabled = false;
+    }
+  });
+
+  const answer = ans.reduce((accumulator, currentValue) => {
+    const sum = getSumFromMul(currentValue.result);
+    return accumulator + sum;
+  }, 0);
+
+  console.log("part-2 answer:", answer);
+};
+
+secondAnswer();