day 2

src/day02/index.ts

@@ -1,35 +1,86 @@
 import run from "aocrunner"
 
-const parseInput = (rawInput: string) => rawInput
+const parseInput = (rawInput: string) => { return rawInput.split('\n').map(line => line.split(' ').map(Number)) }
 
+const acceptableIncreases = [1, 2, 3]
 const part1 = (rawInput: string) => {
   const input = parseInput(rawInput)
+  const differences = input.map(report => {
+    const d = []
+    report.forEach((level, i) => {
+      if (i === 0) return
+      d.push(level - report[i - 1])
+    })
+    return d
+  })
+  let safeCount = 0
+  differences.forEach(report => {
+    const sign = Math.sign(report[0])
+    for (const difference of report) {
+      if (!acceptableIncreases.includes(sign * difference)) {
+        return // report fails
+      }
+    }
+    safeCount++ // made it
+  })
+  return safeCount
+}
 
-  return
+const isSafe = (report: number[], errorsAllowed: 1 | 0): boolean => {
+  const d = [] // differences
+  report.forEach((level, i) => {
+    if (i === 0) { return }
+    d.push(level - report[i - 1])
+  })
+  const sign = Math.sign(d[0])
+  for (const difference of d) {
+    if (acceptableIncreases.includes(sign * difference)) continue
+    if (errorsAllowed === 0) {
+      return false
+    }
+    for (let removalIndex = 0; removalIndex < report.length; removalIndex++) {
+      const fixed = report.toSpliced(removalIndex, 1)
+      if (isSafe(fixed, 0)) { return true }
+    }
+    return false
+  }
+  return true
 }
 
 const part2 = (rawInput: string) => {
   const input = parseInput(rawInput)
-
-  return
+  return input.reduce((acc, report) => {
+    const safe = isSafe(report, 1)
+    return acc + (safe ? 1 : 0)
+  }, 0)
 }
 
 run({
   part1: {
     tests: [
-      // {
-      //   input: ``,
-      //   expected: "",
-      // },
+      {
+        input: `7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9`,
+        expected: 2,
+      },
     ],
     solution: part1,
   },
   part2: {
     tests: [
-      // {
-      //   input: ``,
-      //   expected: "",
-      // },
+      {
+        input: `7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9`,
+        expected: 4,
+      }
     ],
     solution: part2,
   },