Add day 4

days/4/index.js

@@ -0,0 +1,17 @@
+const validatePassword = require('./lib/validatePassword');
+
+const RANGE = [284639, 748759];
+
+let validPasswords = [];
+
+for (let i = RANGE[0]; i <= RANGE[1]; i = i + 1) {
+  console.log(i);
+  if (validatePassword(String(i))) {
+    console.log('VALID!');
+    validPasswords.push(i);
+  }
+}
+
+console.log('validPasswords:');
+console.log(validPasswords);
+console.log(validPasswords.length);

days/4/lib/validatePassword.js

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+// rule 1 = Digits can only increase from left to right
+// rule 2 = The password must contain two consecutive repeat digits that are NOT part of a longer group of repeat digits
+module.exports = function validatePassword(passwordNumber) {
+  let onlyIncreasing = true;
+  let twoAdjacent = false;
+
+  for (let i = 0; i < password.length; i++) {
+    const previousDigit = password[i - 1];
+    const digit = password[i];
+    const nextDigit = password[i + 1];
+    const digitAfterNext = password[i + 2];
+
+    if (previousDigit !== digit && digit === nextDigit && digit !== digitAfterNext) {
+      twoAdjacent = true;
+    }
+
+    if (Number(digit) > Number(nextDigit)) {
+      onlyIncreasing = false;
+    }
+  }
+
+  return twoAdjacent && onlyIncreasing;
+}

days/4/lib/validatePassword.test.js

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+const validatePassword = require('./validatePassword');
+
+it('validates correct passwords', () => {
+  expect(validatePassword(334455)).toBe(true);
+  expect(validatePassword(333445)).toBe(true);
+  expect(validatePassword(288999)).toBe(true);
+  expect(validatePassword(348899)).toBe(true);
+  expect(validatePassword(345899)).toBe(true);
+});
+
+it('invalidates incorrect passwords due to decreasing digits', () => {
+  // Rule 2 Passes = 4
+  expect(validatePassword(334454)).toBe(false);
+  expect(validatePassword(334454)).toBe(false);
+  expect(validatePassword(344561)).toBe(false);
+  expect(validatePassword(345561)).toBe(false);
+  expect(validatePassword(345661)).toBe(false);
+  expect(validatePassword(324467)).toBe(false);
+
+  // Rule 2 Passes < 4
+  expect(validatePassword(300011)).toBe(false);
+  expect(validatePassword(333544)).toBe(false);
+  expect(validatePassword(333244)).toBe(false);
+});
+
+it('invalidates incorrect passwords due to no doubles', () => {
+  expect(validatePassword(345678)).toBe(false);
+  expect(validatePassword(456789)).toBe(false);
+});
+
+it('invalidates incorrect passwords due to only doubles belonging to a longer repeating sequence', () => {
+  expect(validatePassword(333333)).toBe(false);
+  expect(validatePassword(333444)).toBe(false);
+  expect(validatePassword(333456)).toBe(false);
+  expect(validatePassword(345556)).toBe(false);
+  expect(validatePassword(345666)).toBe(false);
+});

days/4/package.json

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+{
+  "name": "4",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "scripts": {
+    "test": "jest"
+  },
+  "devDependencies": {
+    "jest": "^24.9.0"
+  }
+}