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Add Top K Frequent Elements

- Added Top K Frequent Elements and the corresponding tests. - Updated Readme to reflect the same.

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	`1`	`+/*`
	`2`	`+Top K Frequent Elements`
	`3`	`+https://leetcode.com/problems/top-k-frequent-elements/description/`
	`4`	`+`
	`5`	`+Given an integer array nums and an integer k, return the k most frequent elements.`
	`6`	`+You may return the answer in any order.`
	`7`	`+`
	`8`	`+`
	`9`	`+Example 1:`
	`10`	`+`
	`11`	`+Input: nums = [1,1,1,2,2,3], k = 2`
	`12`	`+Output: [1,2]`
	`13`	`+`
	`14`	`+`
	`15`	`+Example 2:`
	`16`	`+`
	`17`	`+Input: nums = [1], k = 1`
	`18`	`+Output: [1]`
	`19`	`+`
	`20`	`+`
	`21`	`+Constraints:`
	`22`	`+`
	`23`	`+1) 1 <= nums.length <= 10^5`
	`24`	`+2) -10^4 <= nums[i] <= 10^4`
	`25`	`+3) k is in the range [1, the number of unique elements in the array].`
	`26`	`+4) It is guaranteed that the answer is unique.`
	`27`	`+*/`
	`28`	`+`
	`29`	`+/**`
	`30`	`+ * @param {number[]} nums`
	`31`	`+ * @param {number} k`
	`32`	`+ * @return {number[]}`
	`33`	`+ */`
	`34`	`+ var topKFrequent = function(nums, k) {`
	`35`	`+ const freqMap = new Map();`
	`36`	`+ const bucket = [];`
	`37`	`+ const result = [];`
	`38`	`+`
	`39`	`+ for(let num of nums) {`
	`40`	`+ freqMap.set(num, (freqMap.get(num) \|\| 0) + 1);`
	`41`	`+ }`
	`42`	`+`
	`43`	`+ for(let [num, freq] of freqMap) {`
	`44`	`+ bucket[freq] = (bucket[freq] \|\| new Set()).add(num);`
	`45`	`+ }`
	`46`	`+`
	`47`	`+ for(let i = bucket.length-1; i >= 0; i--) {`
	`48`	`+ if(bucket[i]) result.push(...bucket[i]);`
	`49`	`+ if(result.length === k) break;`
	`50`	`+ }`
	`51`	`+ return result;`
	`52`	`+};`
	`53`	`+`
	`54`	`+module.exports.topKFrequent = topKFrequent;`

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	`1`	`+const assert = require('assert');`
	`2`	`+const topKFrequent = require('../../LeetcodeProblems/Algorithms/Top_K_Frequent_Elements').topKFrequent;`
	`3`	`+`
	`4`	`+var test = function () {`
	`5`	`+ assert.deepEqual(topKFrequent([1,1,1,2,2,3], 2).sort(), [1,2]);`
	`6`	`+ assert.deepEqual(topKFrequent([7,8,9,8,9,8], 2).sort(), [8,9]);`
	`7`	`+ assert.deepEqual(topKFrequent([1,1,1,1], 1).sort(), [1]);`
	`8`	`+}`
	`9`	`+`
	`10`	`+module.exports.test = test;`

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@@ -67,6 +67,7 @@ To run a specific problem in your console run `node <problem_file_path>` (e.g.
`67`	`67`	`\| [Find Subarrays With Equal Sum ](/LeetcodeProblems/Algorithms/Find_Subarrays_With_Equal_Sums.js) \| Medium \| https://leetcode.com/problems/find-subarrays-with-equal-sum/ \|`
`68`	`68`	`\| [Reverse Integer](/LeetcodeProblems/Algorithms/Reverse_Integer.js) \| Medium \| https://leetcode.com/problems/reverse-integer/ \|`
`69`	`69`	`\| [Minimize Maximum Pair Sum in Array ](/LeetcodeProblems/Algorithms/Minimize_Maximum_Pair_Sum_In_Array.js) \| Medium \| https://leetcode.com/problems/minimize-maximum-pair-sum-in-array/ \|`
	`70`	`+\| [Top K Frequent Elements ](/LeetcodeProblems/Algorithms/Top_K_Frequent_Elements.js) \| Medium \| https://leetcode.com/problems/top-k-frequent-elements/ \|`
`70`	`71`	`\| [Flood Fill ](/LeetcodeProblems/Algorithms/Flood_Fill.js) \| Easy \| https://leetcode.com/problems/flood-fill/ \|`
`71`	`72`	`\| [Implement stack using queues ](/LeetcodeProblems/Algorithms/Implement_stack_using_queues.js) \| Easy \| https://leetcode.com/problems/implement-stack-using-queues/ \|`
`72`	`73`	`\| [Number of Segments in a String ](/LeetcodeProblems/Algorithms/Number_of_Segments_in_a_String.js) \| Easy \| https://leetcode.com/problems/number-of-segments-in-a-string/ \|`

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