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https://github.com/chanda-abdul/dsa-hashmaps

A repository for my Data Structures & Algorithms Hash map drills
https://github.com/chanda-abdul/dsa-hashmaps

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A repository for my Data Structures & Algorithms Hash map drills

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# DSA-Hashmaps



## 1. Create a HashMap class

Walk through the ```HashMap``` implementation in the curriculum and understand it well. Then write a ```HashMap``` class and its core functions with open addressing as the collision resolution mechanism.



Export your ```HashMap``` module

- Create a ```.js``` file called ```HashMaps_drills```. 

- In the file import the ```HashMap``` module. Create a function called ```main()```

- Inside your ```main()``` function, create a hash map called ```lotr```.

- For your hash map that you have created, set the MAX_LOAD_RATIO = 0.5 and SIZE_RATIO = 3.

- Add the following items to your hash map: ```{"Hobbit": "Bilbo"}, {"Hobbit": "Frodo"}, {"Wizard": "Gandalf"}, {"Human": "Aragorn"}, {"Elf": "Legolas"}, {"Maiar": "The Necromancer"}, {"Maiar": "Sauron"}, {"RingBearer": "Gollum"}, {"LadyOfLight": "Galadriel"}, {"HalfElven": "Arwen"}, {"Ent": "Treebeard"}```

- Print your hash map and notice the length and items that are hashed in your hash map. Have you hashed all the items you were asked to?

- Retrieve the value that is hashed in the key ```"Maiar"``` and ```Hobbit```.

- What are the values of ```Maiar``` and ```Hobbit``` that you have? Is there a discrepancy? Explain your answer.

- What is the capacity of your hash table after you have hashed all the above items? Explain your answer.



## 2. WhatDoesThisDo



DO NOT run the following code before solving the problem.



What is the output of the following code? explain your answer.



````

const WhatDoesThisDo = function(){

    let str1 = 'Hello World.';

    let str2 = 'Hello World.';

    let map1 = new HashMap();

    map1.set(str1,10);

    map1.set(str2,20);

    let map2 = new HashMap();

    let str3 = str1;

    let str4 = str2;

    map2.set(str3,20);

    map2.set(str4,10);



    console.log(map1.get(str1));

    console.log(map2.get(str3));

}

````



## 3. Demonstrate understanding of Hash maps

*You don't need to write code for the following two drills. use any drawing app or simple pen and paper *



- 1) Show your hash map after the insertion of keys `10, 22, 31, 4, 15, 28, 17, 88, 59` into a hash map of length `11` using open addressing and a hash function `k` mod `m`, where `k` is the key and `m` is the length.

- 2) Show your hash map after the insertion of the keys `5, 28, 19, 15, 20, 33, 12, 17, 10` into the hash map with collisions resolved by separate chaining. Let the hash table have a length `m = 9`, and let the hash function be `k` mod `m`.



## 4. Remove duplicates

Implement a function to delete all duplicated characters in a string and keep only the first occurrence of each character. For example, if the input is string `“google”`, the result after deletion is `“gole”`. Test your program with a sentence as well such as `"google all that you think can think of"`.



## 5. Any permutation a palindrome

Write an algorithm to check whether any permutation of a string is a palindrome. Given the string `"acecarr"`, the algorithm should return true, because the letters in `"acecarr"` can be rearranged to `"racecar"`, which is a palindrome. In contrast, given the word `"north"`, the algorithm should return false, because there's no way to rearrange those letters to be a palindrome.



## 6. Anagram grouping

Write an algorithm to group a list of words into anagrams. For example, if the input was `['east', 'cars', 'acre', 'arcs', 'teas', 'eats', 'race']`, the output should be: `[['east', 'teas', 'eats'], ['cars', 'arcs'], ['acre', 'race']]`.



## 7. Separate Chaining

Write another hash map implementation as above, but use separate chaining as the collision resolution mechanism.



Test your hash map with the same values from the lotr hash map.