How can I use deque in Python for advanced data manipulation?

How can I use deque in Python for advanced data manipulation?

You can use the collections.deque class for efficient appending and popping from both ends of a list. What specific operations are you interested in?

I want to implement a sliding window algorithm using deque.

You can maintain a deque to store indices of elements in the current window. This allows you to efficiently add and remove elements as the window slides.

Can you provide a code example for that?

Sure! Here's a simple example:

from collections import deque

def sliding_window_max(nums, k):
    if not nums:
        return []
    deq = deque()
    max_nums = []
    for i in range(len(nums)):
        # Remove indices that are out of the current window
        if deq and deq[0] < i - k + 1:
            deq.popleft()
        # Remove indices of smaller elements
        while deq and nums[deq[-1]] < nums[i]:
            deq.pop()
        deq.append(i)
        # Append the maximum for the current window
        if i >= k - 1:
            max_nums.append(nums[deq[0]])
    return max_nums

This function returns the maximum values in each sliding window of size k.

That's great! How does the deque improve performance in this case?

The deque allows for O(1) time complexity for appending and popping elements from both ends, which is crucial for maintaining the sliding window efficiently. This results in an overall O(n) time complexity for the algorithm.