0.Hash-Table.md

Introduce to Hash Table

https://www.tutorialspoint.com/data_structures_algorithms/hash_data_structure.htm

Sets: https://www.w3schools.com/js/js_object_sets.asp

Maps: https://www.w3schools.com/js/js_object_maps.asp

1.sameFrequency.md

sameFrequency

Write a function called sameFrequency. Given two positive integers, find out if the two numbers have the same frequency of digits.

Your solution MUST have the following complexities: Time: O(N)

sameFrequency(182,281) // true
sameFrequency(34,14) // false
sameFrequency(3589578, 5879385) // true
sameFrequency(22,222) // false

2.areThereDuplicates.md

areThereDuplicates

Implement a function called, areThereDuplicates which accepts a variable number of arguments, and checks whether there are any duplicates among the arguments passed in.
You can solve this using the frequency counter pattern OR the multiple pointers pattern.

areThereDuplicates(1, 2, 3) // false
areThereDuplicates(1, 2, 2) // true 
areThereDuplicates('a', 'b', 'c', 'a') // true 

3.avgPair.md

averagePair ( Sliding Window)

Write a function called averagePair. Given a sorted array of integers and a target average, determine if there is a pair of values in the array where the average of the pair equals the target average. There may be more than one pair that matches the average target.

averagePair([1,2,3],2.5) // true
averagePair([1,3,3,5,6,7,10,12,19],8) // true
averagePair([-1,0,3,4,5,6], 4.1) // false
averagePair([],4) // false

4.maxSubarraySum.md

maxSubarraySum ( Sliding Window)

Given an array of integers and a number, write a function called maxSubarraySum, which finds the maximum sum of a subarray with the length of the number passed to the function.

Note that a subarray must consist of consecutive elements from the original array. In the first example below, [100, 200, 300] is a subarray of the original array, but [100, 300] is not.

maxSubarraySum([100,200,300,400], 2) // 700
maxSubarraySum([1,4,2,10,23,3,1,0,20], 4)  // 39 
maxSubarraySum([-3,4,0,-2,6,-1], 2) // 5
maxSubarraySum([3,-2,7,-4,1,-1,4,-2,1],2) // 5
maxSubarraySum([2,3], 3) // null

5. minSubArrayLen.md

minSubArrayLen ( Sliding Window)

Write a function called minSubArrayLen which accepts two parameters - an array of positive integers and a positive integer.

This function should return the minimal length of a contiguous subarray of which the sum is greater than or equal to the integer passed to the function. If there isn't one, return 0 instead.

minSubArrayLen([2,3,1,2,4,3], 7) // 2 -> because [4,3] is the smallest subarray
minSubArrayLen([2,1,6,5,4], 9) // 2 -> because [5,4] is the smallest subarray
minSubArrayLen([3,1,7,11,2,9,8,21,62,33,19], 52) // 1 -> because [62] is greater than 52
minSubArrayLen([1,4,16,22,5,7,8,9,10],39) // 3
minSubArrayLen([1,4,16,22,5,7,8,9,10],55) // 5
minSubArrayLen([4, 3, 3, 8, 1, 2, 3], 11) // 2
minSubArrayLen([1,4,16,22,5,7,8,9,10],95) // 0

Exercises.md

• https://leetcode.com/problems/two-sum/
• https://leetcode.com/problems/contains-duplicate/
• https://leetcode.com/problems/check-if-the-sentence-is-pangram/description/
• https://leetcode.com/problems/first-letter-to-appear-twice/
• https://leetcode.com/problems/check-if-all-characters-have-equal-number-of-occurrences/
• https://leetcode.com/problems/valid-anagram/
• https://leetcode.com/problems/replace-elements-with-greatest-element-on-right-side/
• https://leetcode.com/problems/remove-element/
• https://leetcode.com/problems/isomorphic-strings/

More Exercises (Array):

• https://leetcode.com/problems/counting-elements/description/
• https://leetcode.com/problems/largest-unique-number/description/
• https://leetcode.com/problems/maximum-number-of-balloons/description/