https://leetcode.com/problems/sliding-window-maximum/
Sliding Window Maximum
Given an array nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position.
For example,
Given nums = [1,3,-1,-3,5,3,6,7], and k = 3.
Window position Max --------------- ----- [1 3 -1] -3 5 3 6 7 3 1 [3 -1 -3] 5 3 6 7 3 1 3 [-1 -3 5] 3 6 7 5 1 3 -1 [-3 5 3] 6 7 5 1 3 -1 -3 [5 3 6] 7 6 1 3 -1 -3 5 [3 6 7] 7
Therefore, return the max sliding window as [3,3,5,5,6,7].
Note:
You may assume k is always valid, ie: 1 ≤ k ≤ input array’s size for non-empty array.
Follow up:
Could you solve it in linear time?
Code
from collections import *
class Solution(object):
def maxSlidingWindow(self, nums, k):
"""
:type nums: List[int]
:type k: int
:rtype: List[int]
"""
res = []
# deque of (idx, val)
q = deque()
for i,v in enumerate(nums):
while q and q[0][0] < i-(k-1):
q.popleft()
while q and q[-1][1] < v:
q.pop()
q.append((i, v))
if i >= k-1:
res.append(q[0][1])
return res
Idea
An O(N) time complexity algorithm. Each element is appended to and popped out of the deque at most one time. Idea can be found here: https://leetcode.com/discuss/46578/java-o-n-solution-using-deque-with-explanation