MUYANG GUO / INDEX

LeetCode

LeetCode 239 Sliding Window Maximum - Hard

239. Sliding Window Maximum

·1 min read·#LeetCode#Hard#Python

239. Sliding Window Maximum — Hard

Open on LeetCode

Problem

  1. 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. Return the max sliding window.

Follow up: Could you solve it in linear time?

Example:

Input: nums = [1,3,-1,-3,5,3,6,7], and k = 3 Output: [3,3,5,5,6,7] Explanation:

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

Solution

class Solution:
    def maxSlidingWindow(self, nums, k):
        ### 这道题目用到了doubly linked list的单调栈方法，也就是deque（）的数据结构
        if not nums or not k:
            return []
        
        dq = collections.deque([])
        
        for i in range(k - 1):
            self.push(dq, nums, i)
 
        result = []
        
        for i in range(k - 1, len(nums)):
            self.push(dq, nums, i)
            result.append(nums[dq[0]])
            if dq[0] == i - k + 1:
                dq.popleft()
        
        return result
    
    def push(self, dq, nums, i):
        while dq and nums[dq[-1]] < nums[i]:
            dq.pop()
        dq.append(i)

Comments