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128 lines
3.2 KiB
Python
128 lines
3.2 KiB
Python
class DynamicArray:
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def __init__(self) -> None:
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self.size = 0 # Number of elements in the array
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self.capacity = 1 # Initial capacity of the array
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self.array = [None] * self.capacity # Create an array with initial capacity
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def append(self, item: int) -> None:
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"""
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The function adds an item to the end of the dynamic array.
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Runtime : O(1) amortized
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Space: O(1) amortized
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>>> arr = DynamicArray()
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>>> arr.append(1)
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>>> arr.append(2)
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>>> arr.append(3)
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>>> arr.array[:arr.size] # Display only the filled part of the array
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[1, 2, 3]
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>>> arr.append(4)
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>>> arr.array[:arr.size]
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[1, 2, 3, 4]
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>>> arr.append(5)
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>>> arr.array[:arr.size]
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[1, 2, 3, 4, 5]
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"""
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if self.size == self.capacity:
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self._resize(2 * self.capacity) # Double the capacity
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self.array[self.size] = item
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self.size += 1
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def _resize(self, new_capacity: int) -> None:
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"""
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Resizes the array to the new capacity.
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Runtime : O(n)
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Space: O(n)
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>>> arr = DynamicArray()
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>>> arr.append(1)
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>>> arr.append(2)
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>>> arr._resize(10)
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>>> arr.capacity
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10
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>>> arr.array[:arr.size]
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[1, 2]
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"""
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new_array = [None] * new_capacity
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for i in range(self.size):
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new_array[i] = self.array[i]
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self.array = new_array
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self.capacity = new_capacity
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def get(self, index: int) -> int:
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"""
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The function returns the item at the specified index.
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Runtime : O(1)
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Space: O(1)
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>>> arr = DynamicArray()
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>>> arr.append(1)
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>>> arr.append(2)
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>>> arr.get(0)
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1
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>>> arr.get(1)
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2
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>>> arr.get(2)
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Traceback (most recent call last):
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...
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IndexError: index out of range
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>>> arr.get(-1)
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Traceback (most recent call last):
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...
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IndexError: index out of range
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"""
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if index < 0 or index >= self.size:
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raise IndexError("index out of range")
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return self.array[index]
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def __setitem__(self, index: int, value: int) -> None:
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if index < 0 or index >= self.size:
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raise IndexError("index out of range")
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self.array[index] = value
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def __len__(self) -> int:
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"""
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Returns the number of elements in the dynamic array.
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Runtime : O(1)
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Space: O(1)
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>>> arr = DynamicArray()
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>>> arr.append(1)
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>>> len(arr)
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1
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>>> arr.append(2)
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>>> len(arr)
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2
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>>> arr.append(3)
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>>> len(arr)
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3
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"""
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return self.size
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def __str__(self) -> str:
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"""
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Returns a string representation of the dynamic array.
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>>> arr = DynamicArray()
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>>> arr.append(1)
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>>> arr.append(2)
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>>> arr.append(3)
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>>> str(arr)
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'[1, 2, 3]'
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>>> arr.append(4)
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>>> str(arr)
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'[1, 2, 3, 4]'
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"""
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return "[" + ", ".join(str(self.array[i]) for i in range(self.size)) + "]"
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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