Implementing dynamic array

DIRECTORY.md

@@ -180,6 +180,7 @@
 
 ## Data Structures
   * Arrays
+    * [Dynamic Array](data_structures/arrays/dynamic_array.py)
     * [Equilibrium Index In Array](data_structures/arrays/equilibrium_index_in_array.py)
     * [Find Triplets With 0 Sum](data_structures/arrays/find_triplets_with_0_sum.py)
     * [Index 2D Array In 1D](data_structures/arrays/index_2d_array_in_1d.py)

data_structures/arrays/dynamic_array.py

@@ -0,0 +1,116 @@
+"""
+Author  : Yashwanth Adimulam
+Date    : October 22, 2024
+
+Implement the class of DynamicArray with useful functions based on it.
+References: https://en.wikipedia.org/wiki/Dynamic_array
+            https://www.geeksforgeeks.org/how-do-dynamic-arrays-work/
+
+"""
+
+
+class DynamicArray:
+    def __init__(self) -> None:
+        self.size = 0  # Number of elements in the array
+        self.capacity = 1  # Initial capacity of the array
+        self.array = [None] * self.capacity  # Create an array with initial capacity
+
+    def append(self, item: int) -> None:
+        """
+        The function adds an item to the end of the dynamic array.
+
+        Runtime : O(1) amortized
+        Space: O(1) amortized
+
+        >>> arr = DynamicArray()
+        >>> arr.append(1)
+        >>> arr.append(2)
+        >>> arr.append(3)
+        >>> arr.array[:arr.size]  # Display only the filled part of the array
+        [1, 2, 3]
+        """
+        if self.size == self.capacity:
+            self._resize(2 * self.capacity)  # Double the capacity
+
+        self.array[self.size] = item
+        self.size += 1
+
+    def _resize(self, new_capacity: int) -> None:
+        """
+        Resizes the array to the new capacity.
+
+        Runtime : O(n)
+        Space: O(n)
+
+        >>> arr = DynamicArray()
+        >>> arr.append(1)
+        >>> arr.append(2)
+        >>> arr.append(3)
+        >>> arr._resize(10)
+        >>> arr.capacity
+        10
+        """
+        new_array = [None] * new_capacity
+        for i in range(self.size):
+            new_array[i] = self.array[i]
+        self.array = new_array
+        self.capacity = new_capacity
+
+    def get(self, index: int) -> int:
+        """
+        The function returns the item at the specified index.
+
+        Runtime : O(1)
+        Space: O(1)
+
+        >>> arr = DynamicArray()
+        >>> arr.append(1)
+        >>> arr.append(2)
+        >>> arr.get(0)
+        1
+        >>> arr.get(1)
+        2
+        >>> arr.get(2)
+        Traceback (most recent call last):
+        ...
+        IndexError: index out of range
+        """
+        if index < 0 or index >= self.size:
+            raise IndexError("index out of range")
+        return self.array[index]
+
+    def __len__(self) -> int:
+        """
+        Returns the number of elements in the dynamic array.
+
+        Runtime : O(1)
+        Space: O(1)
+
+        >>> arr = DynamicArray()
+        >>> arr.append(1)
+        >>> len(arr)
+        1
+        >>> arr.append(2)
+        >>> len(arr)
+        2
+        """
+        return self.size
+
+    def __str__(self) -> str:
+        """
+        Returns a string representation of the dynamic array.
+
+        >>> arr = DynamicArray()
+        >>> arr.append(1)
+        >>> arr.append(2)
+        >>> arr.append(3)
+        >>> str(arr)
+        '[1, 2, 3]'
+        """
+        return "[" + ", ".join(str(self.array[i]) for i in range(self.size)) + "]"
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()