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@@ -0,0 +1,73 @@
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+import { loadInput, numericAscSort, strToInt } from "../common.js";
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+
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+// const input = loadInput("./2/test.input", parseInput, true);
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+const input = loadInput(2, parseInput);
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+
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+solve(input);
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+
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+/**
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+ * @param {string} inputData
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+ * @returns {number[]}
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+ */
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+function parseInput(inputData) {
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+ const reports = inputData.split(/\n/).map((report) => report.split(" ").map(strToInt));
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+
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+ return reports;
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+}
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+
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+/**
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+ * @param {number[]} parsedInput
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+ */
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+function solve(parsedInput) {
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+ let safeReports = 0;
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+
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+ for(const report of parsedInput) {
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+ let currDirection = 0;
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+ let lastDirection = 0;
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+ /**
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+ * Whether or not the report is safe
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+ *
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+ * Report is only safe when the data is sorted in one direction, and
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+ * each value is no less than 1 value away, and no more than 3 values
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+ * away from each other.
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+ *
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+ * e.g.
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+ * ```
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+ * 1,2,3,4,5 safe
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+ * 5,4,3,2,1 safe
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+ * 1,2,3,2,1 unsafe
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+ * 1,2,4,5,6 safe
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+ * 1,2,7,8,9 unsafe
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+ * ```
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+ */
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+ let safe = false;
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+
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+ // Safety check written this way to make troubleshooting easier
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+ for(let i = 0; i < report.length - 1; i++) {
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+ currDirection = numericAscSort(report[i], report[i + 1]);
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+ const difference = Math.abs(report[i] - report[i + 1]);
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+
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+ // Check if the direction has changed, but skip the first round
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+ // Also catches if there were no differences between the two numbers
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+ if(i != 0 && lastDirection != currDirection) {
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+ safe = false;
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+ break;
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+ }
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+ // Make sure the difference wasn't too great
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+ else if(difference > 3) {
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+ safe = false;
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+ break;
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+ }
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+ else {
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+ safe = true;
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+ }
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+
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+ lastDirection = currDirection;
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+ }
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+
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+ if(safe) { safeReports++; }
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+ }
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+
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+ // Not: ^400, ^391
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+ console.log("Safe Reports:", safeReports);
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+}
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