Complete part1 and begin part 2

Author: DrantDumani

red_nosed_reports/part1.js

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+// every sequence must follow two rules
+// sequence must be either all increasing or all decreasing from left to right
+// adjacent numbers must differ by at least 1 or at most 3.
+
+// split up input line by line
+// loop through input
+// for every line, split up that input by space
+// if there is no sequence, find out if the difference btwn first two numbers violates the difference rule
+// then set the sequence
+// if there is a sequence find out if the two numbers violate that rule, then do the above.
+
+const fs = require("fs");
+const input = fs.readFileSync("./input.txt", "utf8").split(/\n/);
+
+function findUnsafe(reports) {
+  let safe = 0;
+  for (let i = 0; i < reports.length; i++) {
+    let currSeq = 0;
+    let isSafe = true;
+    const levels = reports[i].split(/\s/).map((el) => Number(el));
+    for (let j = 1; j < levels.length; j++) {
+      if (!currSeq) {
+        currSeq = levels[j] > levels[j - 1] ? 1 : -1;
+      }
+      const diff = Math.abs(levels[j - 1] - levels[j]);
+      if (diff < 1 || diff > 3) {
+        isSafe = false;
+        break;
+      }
+      if (
+        (currSeq === -1 && levels[j] > levels[j - 1]) ||
+        (currSeq === 1 && levels[j] < levels[j - 1])
+      ) {
+        isSafe = false;
+        break;
+      }
+    }
+    if (isSafe) safe += 1;
+  }
+  return safe;
+}
+
+console.log(findUnsafe(input));

red_nosed_reports/part2.js

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+const fs = require("fs");
+const input = fs.readFileSync("./input.txt", "utf8").split("\n");
+
+function findSafe(reports) {
+  let safe = 0;
+  for (let report of reports) {
+    const levels = report.split(/\s/).map((el) => Number(el));
+    const stack = [];
+    let dampener = false;
+    let isSafe = true;
+    let inc = 0;
+    let dec = 0;
+    for (let i = levels.length - 1; i - 1 >= 0; i--) {
+      if (levels[i] > levels[i - 1]) inc += 1;
+      else if (levels[i] < levels[i - 1]) dec += 1;
+    }
+    if (inc === dec) {
+      // report is unsafe. Move to the next one
+      continue;
+    }
+    const seqDir = inc > dec ? "inc" : "dec";
+
+    stack.push(levels.pop());
+    while (levels.length > 1) {
+      if (
+        !checkSafety(stack[stack.length - 1], levels[levels.length - 1], seqDir)
+      ) {
+        if (dampener) {
+          isSafe = false;
+          break;
+        } else {
+          dampener = true;
+          if (
+            checkSafety(
+              stack[stack.length - 1],
+              levels[levels.length - 2],
+              seqDir
+            )
+          ) {
+            levels.pop();
+          } else {
+            stack.pop();
+          }
+        }
+      } else {
+        stack.push(levels.pop());
+      }
+    }
+
+    // console.log(report, isSafe, seqDir);
+    if (isSafe) safe += 1;
+  }
+  return safe;
+}
+
+function checkSafety(prevNum, nextNum, direction) {
+  let currDir = "";
+  if (prevNum > nextNum) {
+    currDir = "inc";
+  } else if (prevNum < nextNum) {
+    currDir = "dec";
+  }
+
+  let diff = Math.abs(prevNum - nextNum);
+
+  if (diff < 1 || diff > 3 || currDir !== direction) {
+    return false;
+  }
+  return true;
+}
+
+console.log(findSafe(input));