2023.08

challenges/2023/08.js

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+// Part 1
+const solvePuzzle1 = (input) => {
+  const lines = input.split('\n').filter((l) => !!l[0]);
+  const [instructions] = lines;
+
+  const nodes = {};
+  addNodes(nodes, lines.slice(1));
+
+  const [steps] = findSteps(['AAA'], instructions, nodes, (place) => place !== 'ZZZ');
+  return steps;
+};
+
+// Part 2
+const solvePuzzle2 = (input) => {
+  const lines = input.split('\n').filter((l) => !!l[0]);
+  const [instructions] = lines;
+
+  const nodes = {};
+  addNodes(nodes, lines.slice(1));
+
+  const startingPlaces = Object.keys(nodes).filter((place) => place[2] === 'A');
+  const endingSteps = findSteps(startingPlaces, instructions, nodes, (place) => place[2] !== 'Z');
+  return lcmOfArray(endingSteps);
+};
+
+const addNodes = (nodes, mapping) => {
+  mapping.forEach((line) => {
+    const [place, leftRight] = line.split(' = ');
+    nodes[place] = leftRight.replaceAll(/[^A-Z0-9,]/g, '').split(',');
+  });
+};
+
+const findSteps = (startingPlaces, instructions, nodes, assertion) => {
+  const endingSteps = [];
+
+  startingPlaces.forEach((place) => {
+    let currentPlace = place;
+    let currentInstructionsStep = 0;
+    let steps = 0;
+
+    while (assertion(currentPlace)) {
+      const currentDirection = instructions[currentInstructionsStep];
+      currentPlace = nodes[currentPlace][currentDirection === 'L' ? 0 : 1];
+      steps += 1;
+      currentInstructionsStep += 1;
+
+      if (currentInstructionsStep === instructions.length) {
+        currentInstructionsStep = 0;
+      }
+    }
+
+    endingSteps.push(steps);
+  });
+
+  return endingSteps;
+};
+
+const gcd = (a, b) => {
+  while (b !== 0) {
+    const prev = b;
+    b = a % b;
+    a = prev;
+  }
+
+  return a;
+};
+
+const lcmOfArray = (numbers) => {
+  let result = numbers[0];
+
+  for (let i = 1; i < numbers.length; i++) {
+    const currentNumber = numbers[i];
+    const currentGcd = gcd(result, currentNumber);
+
+    result = (result * currentNumber) / currentGcd;
+  }
+
+  return result;
+};
+
+require(__dirname + '/../../utils/test.js').test(__filename, __dirname, solvePuzzle1, '1');
+require(__dirname + '/../../utils/test.js').test(__filename, __dirname, solvePuzzle2, '2');