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Solve problem: First Bad Version & Binary Search
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‎README.MD

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## Problems
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| Title | Solution | Difficulty |
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|--------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------|------------|
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| [Contains Duplicate](https://leetcode.com/problems/contains-duplicate) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/containsDuplicate/index.js) | Easy |
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| [Missing Number](https://leetcode.com/problems/missing-number) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/tree/main/solutions/missingNumber/index.js) | Easy |
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| [Find All Numbers Disappeared in an Array](https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/findDisappearedNumbers/index.js) | Easy |
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| [Single Number](https://leetcode.com/problems/single-number) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/singleNumber/index.js) | Easy |
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| [Climbing Stairs](https://leetcode.com/problems/climbing-stairs) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/climbStairs/index.js) | Easy |
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| [Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/maxProfit/index.js) | Easy |
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| [Range Sum Query - Immutable](https://leetcode.com/problems/range-sum-query-immutable) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/sumRange/index.js) | Easy |
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| [Counting Bits](https://leetcode.com/problems/counting-bits) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/countBits/index.js) | Easy |
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| [Linked List Cycle](https://leetcode.com/problems/linked-list-cycle) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/hasCycle/index.js) | Easy |
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| [Middle of the Linked List](https://leetcode.com/problems/middle-of-the-linked-list) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/middleNode/index.js) | Easy |
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| [Reverse Linked List](https://leetcode.com/problems/reverse-linked-list) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/reverseList/index.js) | Easy |
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| [Palindrome Linked List](https://leetcode.com/problems/palindrome-linked-list) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/isPalindrome/index.js) | Easy |
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| [Remove Linked List Elements](https://leetcode.com/problems/remove-linked-list-elements) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/removeElements/index.js) | Easy |
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| [Two Sum](https://leetcode.com/problems/two-sum) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/twoSum/index.js) | Easy |
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| [Majority Element](https://leetcode.com/problems/majority-element) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/majorityElement/index.js) | Easy |
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| [Running Sum of 1d Array](https://leetcode.com/problems/running-sum-of-1d-array/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/runningSum/index.js) | Easy |
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| [Find Pivot Index](https://leetcode.com/problems/find-pivot-index/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/pivotIndex/index.js) | Easy |
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| [Is Subsequence](https://leetcode.com/problems/is-subsequence/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/isSubsequence/isSubsequence.js) | Easy |
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| [Isomorphic Strings](https://leetcode.com/problems/isomorphic-strings/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/isIsomorphic/isIsomorphic.js) | Easy |
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| [Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/mergeTwoLists/mergeTwoLists.js) | Easy |
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| [Longest Palindrome](https://leetcode.com/problems/longest-palindrome/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/longestPalindrome/longestPalindrome.js) | Easy |
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| [N-ary Tree Preorder Traversal](https://leetcode.com/problems/n-ary-tree-preorder-traversal/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/preorder/preorder.js) | Easy |
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| [Linked List Cycle II](https://leetcode.com/problems/linked-list-cycle-ii/description/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/detectCycle/detectCycle.js) | Medium |
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| Title | Solution | Difficulty |
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|--------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------|------------|
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| [Contains Duplicate](https://leetcode.com/problems/contains-duplicate) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/containsDuplicate/index.js) | Easy |
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| [Missing Number](https://leetcode.com/problems/missing-number) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/tree/main/solutions/missingNumber/index.js) | Easy |
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| [Find All Numbers Disappeared in an Array](https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/findDisappearedNumbers/index.js) | Easy |
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| [Single Number](https://leetcode.com/problems/single-number) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/singleNumber/index.js) | Easy |
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| [Climbing Stairs](https://leetcode.com/problems/climbing-stairs) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/climbStairs/index.js) | Easy |
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| [Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/maxProfit/index.js) | Easy |
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| [Range Sum Query - Immutable](https://leetcode.com/problems/range-sum-query-immutable) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/sumRange/index.js) | Easy |
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| [Counting Bits](https://leetcode.com/problems/counting-bits) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/countBits/index.js) | Easy |
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| [Linked List Cycle](https://leetcode.com/problems/linked-list-cycle) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/hasCycle/index.js) | Easy |
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| [Middle of the Linked List](https://leetcode.com/problems/middle-of-the-linked-list) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/middleNode/index.js) | Easy |
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| [Reverse Linked List](https://leetcode.com/problems/reverse-linked-list) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/reverseList/index.js) | Easy |
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| [Palindrome Linked List](https://leetcode.com/problems/palindrome-linked-list) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/isPalindrome/index.js) | Easy |
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| [Remove Linked List Elements](https://leetcode.com/problems/remove-linked-list-elements) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/removeElements/index.js) | Easy |
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| [Two Sum](https://leetcode.com/problems/two-sum) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/twoSum/index.js) | Easy |
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| [Majority Element](https://leetcode.com/problems/majority-element) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/majorityElement/index.js) | Easy |
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| [Running Sum of 1d Array](https://leetcode.com/problems/running-sum-of-1d-array/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/runningSum/index.js) | Easy |
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| [Find Pivot Index](https://leetcode.com/problems/find-pivot-index/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/pivotIndex/index.js) | Easy |
26+
| [Is Subsequence](https://leetcode.com/problems/is-subsequence/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/isSubsequence/isSubsequence.js) | Easy |
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| [Isomorphic Strings](https://leetcode.com/problems/isomorphic-strings/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/isIsomorphic/isIsomorphic.js) | Easy |
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| [Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/mergeTwoLists/mergeTwoLists.js) | Easy |
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| [Longest Palindrome](https://leetcode.com/problems/longest-palindrome/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/longestPalindrome/longestPalindrome.js) | Easy |
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| [N-ary Tree Preorder Traversal](https://leetcode.com/problems/n-ary-tree-preorder-traversal/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/preorder/preorder.js) | Easy |
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| [First Bad Version](https://leetcode.com/problems/first-bad-version/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/findFirstBadVersion/findFirstBadVersion.js) | Easy |
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| [Binary Search](https://leetcode.com/problems/binary-search/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/binarySearch/binarySearch.js) | Easy |
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| [Linked List Cycle II](https://leetcode.com/problems/linked-list-cycle-ii/description/) | [Solution](https://github.com/GolubevDS/LeetCodePatterns/blob/main/solutions/detectCycle/detectCycle.js) | Medium |

‎solutions/binarySearch/README.MD

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## [704. Binary Search](https://leetcode.com/problems/binary-search/)
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Given an array of integers `nums` which is sorted in ascending order, and an integer `target`, write a function to search `target` in `nums`. If `target` exists, then return its index. Otherwise, return `-1`.
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You must write an algorithm with `O(log n)` runtime complexity.

‎solutions/binarySearch/binarySearch.js

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/**
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* @param {number[]} nums
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* @param {number} target
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* @return {number}
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*/
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function binarySearch(nums, target) {
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let start = 0,
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end = nums.length - 1;
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while (start <= end) {
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const index = Math.floor((start + end) / 2)
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if (nums[index] === target) return index;
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if (nums[index] > target) end = index - 1;
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if (nums[index] < target) start = index + 1;
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}
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return -1;
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}
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module.exports = binarySearch;

‎solutions/binarySearch/binarySearch.spec.js

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const binarySearch = require('./binarySearch');
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describe('Binary Search', () => {
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it('should return the index of the target element', () => {
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expect(binarySearch([1, 3, 5, 7, 9], 3)).toBe(1);
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expect(binarySearch([1, 3, 5, 7, 9], 9)).toBe(4);
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expect(binarySearch([1, 3, 5, 7, 9], 1)).toBe(0);
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expect(binarySearch([1, 3, 5, 7, 9], 5)).toBe(2);
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expect(binarySearch([1, 3, 5, 7, 9], 7)).toBe(3);
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});
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it('should return -1 if the target element is not found', () => {
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expect(binarySearch([1, 3, 5, 7, 9], 2)).toBe(-1);
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expect(binarySearch([1, 3, 5, 7, 9], 0)).toBe(-1);
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expect(binarySearch([1, 3, 5, 7, 9], 10)).toBe(-1);
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});
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it('should return -1 for an empty array', () => {
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expect(binarySearch([], 1)).toBe(-1);
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});
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});

‎solutions/findFirstBadVersion/README.MD

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## [278. First Bad Version](https://leetcode.com/problems/first-bad-version/)
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You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad.
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Suppose you have `n` versions `[1, 2, ..., n]` and you want to find out the first bad one, which causes all the following ones to be bad.
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You are given an API `bool isBadVersion(version)` which returns whether `version` is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.

‎solutions/findFirstBadVersion/findFirstBadVersion.js

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/**
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* @param {function} isBadVersion()
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* @return {function}
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*/
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function findFirstBadVersion(isBadVersion) {
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/**
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* @param {number} n Total versions
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* @return {number} The first bad version
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*/
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return function (n) {
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let start = 1,
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end = n;
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while (end > start) {
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const middle = Math.floor((start + end) / 2),
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isMiddleBad = isBadVersion(middle);
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if (isMiddleBad && !isBadVersion(middle - 1)) return middle;
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isMiddleBad
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? end = middle
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: start = middle + 1;
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}
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return start;
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};
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}
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module.exports = findFirstBadVersion;

‎solutions/findFirstBadVersion/findFirstBadVersion.spec.js

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const findFirstBadVersion = require('./findFirstBadVersion');
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describe('First Bad Version', () => {
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it('should return the first bad version', () => {
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const isBadVersion = (version) => version >= 4;
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const solution = findFirstBadVersion(isBadVersion)(10);
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expect(solution).toEqual(4);
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});
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it('should return the first bad version when there is only one version', () => {
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const isBadVersion = (version) => version === 1;
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const solution = findFirstBadVersion(isBadVersion)(1);
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expect(solution).toEqual(1);
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});
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it('should return the first bad version when the bad version is the last one', () => {
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const isBadVersion = (version) => version === 10;
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const solution = findFirstBadVersion(isBadVersion)(10);
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expect(solution).toEqual(10);
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});
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});
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