diff --git a/data_structures/queue/monotonic_queue.py b/data_structures/queue/monotonic_queue.py new file mode 100644 index 000000000000..b19672fd7e66 --- /dev/null +++ b/data_structures/queue/monotonic_queue.py @@ -0,0 +1,39 @@ +from __future__ import annotations + +from collections import deque + +arr = [1, 3, -1, -3, 5, 3, 6, 7] +window_size = 3 +expect = [3, 3, 5, 5, 6, 7] + + +def max_sliding_window(arr: list[float], window_size: int) -> list[float]: + """ + Given an array of integers nums, there is a sliding window of size k which is moving + from the very left of the array to the very right. + Each time the sliding window of length window_size moves right by one position. + Return the max sliding window. + >>> max_sliding_window(arr, window_size) == expect + True + """ + max_val = [] + mono_queue: deque = deque() + for i in range(len(arr)): + # pop the element if the index is outside the window size k + if mono_queue and i - mono_queue[0] >= window_size: + mono_queue.popleft() + # keep the queue monotonically decreasing + # so that the max value is always on the top + while mono_queue and arr[i] >= arr[mono_queue[-1]]: + mono_queue.pop() + mono_queue.append(i) + # the maximum value is the first element in queue + if i >= window_size - 1: + max_val.append(arr[mono_queue[0]]) + return max_val + + +if __name__ == "__main__": + from doctest import testmod + + testmod()