Solve 2024-02

2024/02/index.ts

@@ -0,0 +1,43 @@
+const isSafe = (numbers: number[]) => {
+  const increasing = numbers[1] - numbers[0];
+
+  for (let i = 1; i < numbers.length; i++) {
+    const signedDiff = numbers[i] - numbers[i - 1];
+    if (signedDiff < 0 !== increasing < 0) {
+      return false;
+    }
+
+    const diff = Math.abs(signedDiff);
+    if (diff < 1 || diff > 3) {
+      return false;
+    }
+  }
+
+  return true;
+};
+
+export function solveFirst(input: string): number {
+  const lines = input.split('\n').map((line) => line.split(' ').map(Number));
+
+  return lines.filter(isSafe).length;
+}
+
+export function solveSecond(input: string): number {
+  const lines = input.split('\n').map((line) => line.split(' ').map(Number));
+
+  const safe = lines.filter((numbers) => {
+    if (isSafe(numbers)) {
+      return true;
+    }
+
+    for (let i = 0; i < numbers.length; i++) {
+      if (isSafe(numbers.toSpliced(i, 1))) {
+        return true;
+      }
+    }
+
+    return false;
+  });
+
+  return safe.length;
+}