HashMaps/hash_map_sc.py

# Name: Andrew Scott
# OSU Email: scottand@oregonstate.edu
# Course: CS261 - Data Structures
# Assignment: 6
# Due Date: 2022-06-03
# Description: HashMap implementation using Separate Chaining


from a6_include import DynamicArray, LinkedList, SLNode, hash_function_1, hash_function_2


class HashMap:
    def __init__(self, capacity: int, function) -> None:
        """
        Initialize new HashMap that uses
        separate chaining for collision resolution
        DO NOT CHANGE THIS METHOD IN ANY WAY
        """
        self._buckets = DynamicArray()
        for _ in range(capacity):
            self._buckets.append(LinkedList())

        self._capacity = capacity
        self._hash_function = function
        self._size = 0

    def __str__(self) -> str:
        """
        Override string method to provide more readable output
        DO NOT CHANGE THIS METHOD IN ANY WAY
        """
        out = ""
        for i in range(self._buckets.length()):
            out += str(i) + ": " + str(self._buckets[i]) + "\n"
        return out

    def get_size(self) -> int:
        """
        Return size of map
        DO NOT CHANGE THIS METHOD IN ANY WAY
        """
        return self._size

    def get_capacity(self) -> int:
        """
        Return capacity of map
        DO NOT CHANGE THIS METHOD IN ANY WAY
        """
        return self._capacity

    # ------------------------------------------------------------------ #

    def put(self, key: str, value: object) -> None:
        """Adds (or updates) a key/value pair to the hash map

        Parameters
        ----------
        key : str
            Identifier for the given value
        value : object
            Value to add, or update if the key is already present
        """

        hash = self._hash_function(key)
        index = hash % self._capacity
        node = self._buckets[index].contains(key)
        # create new key/value pair if key does not exist
        if node is None:
            self._buckets[index].insert(key, value)
            self._size += 1
        # update value if key already exists
        else:
            node.value = value

    def empty_map_put(self, index_array, key: str, value: object) -> DynamicArray:
        """Alternative to put() with reduced time complexity for empty hash maps

        Note that unlike put() this method allows duplicates for the purpose of
        finding the mode and frequency of values added to the hash map.

        Parameters
        ----------
        key : str
            Indentifier for the given value
        value : object
            Value to add
        """

        hash = self._hash_function(key)
        index = hash % self._capacity
        index_array.append(index)
        self._buckets[index].insert(key, value)
        return index_array

    def empty_buckets(self) -> int:
        """Gets the number of empty buckets in the hash table

        Returns
        -------
        int
            Number of empty buckets
        """

        count = 0
        for i in range(self._capacity):
            if self._buckets[i].length() == 0:
                count += 1
        return count

    def table_load(self) -> float:
        """Get the current hash table load factor

        Returns
        -------
        float
            The load factor
        """

        return self._size / self._capacity

    def clear(self) -> None:
        """Clear the contents of the hash map without changing its capacity"""
        for i in range(self._capacity):
            if self._buckets[i].length() != 0:
                self._buckets[i] = LinkedList()
        self._size = 0


    def resize_table(self, new_capacity: int) -> None:
        """Changes the capacity of the hash table

        All existing key/value pairs remain and are rehashed. Does nothing if
        the new capacity is less than 1.

        Parameters
        ----------
        new_capacity : int
            New capacity for the hash table
        """

        # immediately return if new_capacity is less than 1
        if new_capacity < 1:
            return
        # create new hash table if new_capacity is 1 or greater
        new_table = DynamicArray()
        for i in range(new_capacity):
            new_table.append(LinkedList())
        # rehash and move values from current to new hash table
        for i in range(self._capacity):
            linked_list = self._buckets[i]
            if linked_list.length() != 0:
                for node in linked_list:
                    hash = self._hash_function(node.key)
                    index = hash % new_capacity
                    new_table[index].insert(node.key, node.value)
        # assign the new table and capacity to the existing HashMap object
        self._buckets = new_table
        self._capacity = new_capacity

    def get(self, key: str) -> object:
        """Get the value associated with the given key

        Parameters
        ----------
        key : str
            Key to look up in the hash map

        Returns
        -------
        object
            The value associated with the key, or None if the key does not exist
        """

        hash = self._hash_function(key)
        index = hash % self._capacity
        node = self._buckets[index].contains(key)
        if node is None:
            return node
        return node.value

    def contains_key(self, key: str) -> bool:
        """Checks if a given key is in the hash map

        Parameters
        ----------
        key : str
            Key to look up in the hash map

        Returns
        -------
        bool
            True if the key is in the hash map, otherwise False
        """

        # immediately return if the hash map is empty
        if self._size == 0:
            return False
        # proceed to check for key in non-empty hash map
        hash = self._hash_function(key)
        index = hash % self._capacity
        node = self._buckets[index].contains(key)
        if node is not None:
            return True
        return False


    def remove(self, key: str) -> None:
        """Removes a key/value pair from the hash map

        Parameters
        ----------
        key : str
            Key to look up in the hash map
        """

        hash = self._hash_function(key)
        index = hash % self._capacity
        is_removed = self._buckets[index].remove(key)
        if is_removed:
            self._size -= 1

    def get_keys(self) -> DynamicArray:
        """Get an array that contains all the keys in the hash map

        Returns
        -------
        DynamicArray
            Array containing the hash maps keys
        """

        keys = DynamicArray()
        for i in range(self._capacity):
            linked_list = self._buckets[i]
            for node in linked_list:
                keys.append(node.key)
        return keys


def find_mode(da: DynamicArray) -> (DynamicArray, int):
    """
    TODO: Write this implementation
    """
    # if you'd like to use a hash map,
    # use this instance of your Separate Chaining HashMap
    map = HashMap(da.length() // 3, hash_function_1)

    pass




# ------------------- BASIC TESTING ---------------------------------------- #

if __name__ == "__main__":

    print("\nPDF - put example 1")
    print("-------------------")
    m = HashMap(50, hash_function_1)
    for i in range(150):
        m.put("str" + str(i), i * 100)
        if i % 25 == 24:
            print(m.empty_buckets(), m.table_load(), m.get_size(), m.get_capacity())

    print("\nPDF - put example 2")
    print("-------------------")
    m = HashMap(40, hash_function_2)
    for i in range(50):
        m.put("str" + str(i // 3), i * 100)
        if i % 10 == 9:
            print(m.empty_buckets(), m.table_load(), m.get_size(), m.get_capacity())

    print("\nPDF - empty_buckets example 1")
    print("-----------------------------")
    m = HashMap(100, hash_function_1)
    print(m.empty_buckets(), m.get_size(), m.get_capacity())
    m.put("key1", 10)
    print(m.empty_buckets(), m.get_size(), m.get_capacity())
    m.put("key2", 20)
    print(m.empty_buckets(), m.get_size(), m.get_capacity())
    m.put("key1", 30)
    print(m.empty_buckets(), m.get_size(), m.get_capacity())
    m.put("key4", 40)
    print(m.empty_buckets(), m.get_size(), m.get_capacity())

    print("\nPDF - empty_buckets example 2")
    print("-----------------------------")
    m = HashMap(50, hash_function_1)
    for i in range(150):
        m.put("key" + str(i), i * 100)
        if i % 30 == 0:
            print(m.empty_buckets(), m.get_size(), m.get_capacity())

    print("\nPDF - table_load example 1")
    print("--------------------------")
    m = HashMap(100, hash_function_1)
    print(m.table_load())
    m.put("key1", 10)
    print(m.table_load())
    m.put("key2", 20)
    print(m.table_load())
    m.put("key1", 30)
    print(m.table_load())

    print("\nPDF - table_load example 2")
    print("--------------------------")
    m = HashMap(50, hash_function_1)
    for i in range(50):
        m.put("key" + str(i), i * 100)
        if i % 10 == 0:
            print(m.table_load(), m.get_size(), m.get_capacity())

    print("\nPDF - clear example 1")
    print("---------------------")
    m = HashMap(100, hash_function_1)
    print(m.get_size(), m.get_capacity())
    m.put("key1", 10)
    m.put("key2", 20)
    m.put("key1", 30)
    print(m.get_size(), m.get_capacity())
    m.clear()
    print(m.get_size(), m.get_capacity())

    print("\nPDF - clear example 2")
    print("---------------------")
    m = HashMap(50, hash_function_1)
    print(m.get_size(), m.get_capacity())
    m.put("key1", 10)
    print(m.get_size(), m.get_capacity())
    m.put("key2", 20)
    print(m.get_size(), m.get_capacity())
    m.resize_table(100)
    print(m.get_size(), m.get_capacity())
    m.clear()
    print(m.get_size(), m.get_capacity())

    print("\nPDF - resize example 1")
    print("----------------------")
    m = HashMap(20, hash_function_1)
    m.put("key1", 10)
    print(m.get_size(), m.get_capacity(), m.get("key1"), m.contains_key("key1"))
    m.resize_table(30)
    print(m.get_size(), m.get_capacity(), m.get("key1"), m.contains_key("key1"))

    print("\nPDF - resize example 2")
    print("----------------------")
    m = HashMap(75, hash_function_2)
    keys = [i for i in range(1, 1000, 13)]
    for key in keys:
        m.put(str(key), key * 42)
    print(m.get_size(), m.get_capacity())

    for capacity in range(111, 1000, 117):
        m.resize_table(capacity)

        m.put("some key", "some value")
        result = m.contains_key("some key")
        m.remove("some key")

        for key in keys:
            # all inserted keys must be present
            result &= m.contains_key(str(key))
            # NOT inserted keys must be absent
            result &= not m.contains_key(str(key + 1))
        print(
            capacity, result, m.get_size(), m.get_capacity(), round(m.table_load(), 2)
        )

    print("\nPDF - get example 1")
    print("-------------------")
    m = HashMap(30, hash_function_1)
    print(m.get("key"))
    m.put("key1", 10)
    print(m.get("key1"))

    print("\nPDF - get example 2")
    print("-------------------")
    m = HashMap(150, hash_function_2)
    for i in range(200, 300, 7):
        m.put(str(i), i * 10)
    print(m.get_size(), m.get_capacity())
    for i in range(200, 300, 21):
        print(i, m.get(str(i)), m.get(str(i)) == i * 10)
        print(i + 1, m.get(str(i + 1)), m.get(str(i + 1)) == (i + 1) * 10)

    print("\nPDF - contains_key example 1")
    print("----------------------------")
    m = HashMap(10, hash_function_1)
    print(m.contains_key("key1"))
    m.put("key1", 10)
    m.put("key2", 20)
    m.put("key3", 30)
    print(m.contains_key("key1"))
    print(m.contains_key("key4"))
    print(m.contains_key("key2"))
    print(m.contains_key("key3"))
    m.remove("key3")
    print(m.contains_key("key3"))

    print("\nPDF - contains_key example 2")
    print("----------------------------")
    m = HashMap(75, hash_function_2)
    keys = [i for i in range(1, 1000, 20)]
    for key in keys:
        m.put(str(key), key * 42)
    print(m.get_size(), m.get_capacity())
    result = True
    for key in keys:
        # all inserted keys must be present
        result &= m.contains_key(str(key))
        # NOT inserted keys must be absent
        result &= not m.contains_key(str(key + 1))
    print(result)

    print("\nPDF - remove example 1")
    print("----------------------")
    m = HashMap(50, hash_function_1)
    print(m.get("key1"))
    m.put("key1", 10)
    print(m.get("key1"))
    m.remove("key1")
    print(m.get("key1"))
    m.remove("key4")

    print("\nPDF - get_keys example 1")
    print("------------------------")
    m = HashMap(10, hash_function_2)
    for i in range(100, 200, 10):
        m.put(str(i), str(i * 10))
    print(m.get_keys())

    m.resize_table(1)
    print(m.get_keys())

    m.put("200", "2000")
    m.remove("100")
    m.resize_table(2)
    print(m.get_keys())

    print("\nPDF - find_mode example 1")
    print("-----------------------------")
    da = DynamicArray(["apple", "apple", "grape", "melon", "melon", "peach"])
    map = HashMap(da.length() // 3, hash_function_1)
    mode, frequency = find_mode(da)
    print(f"Input: {da}\nMode: {mode}, Frequency: {frequency}")

    print("\nPDF - find_mode example 2")
    print("-----------------------------")
    test_cases = (
        [
            "Arch",
            "Manjaro",
            "Manjaro",
            "Mint",
            "Mint",
            "Mint",
            "Ubuntu",
            "Ubuntu",
            "Ubuntu",
            "Ubuntu",
        ],
        ["one", "two", "three", "four", "five"],
        ["2", "4", "2", "6", "8", "4", "1", "3", "4", "5", "7", "3", "3", "2"],
    )

    for case in test_cases:
        da = DynamicArray(case)
        map = HashMap(da.length() // 3, hash_function_2)
        mode, frequency = find_mode(da)
        print(f"Input: {da}\nMode: {mode}, Frequency: {frequency}\n")