[Leetcode] #239 Sliding Window Maximum

最新推荐文章于 2021-11-04 14:36:47 发布

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最新推荐文章于 2021-11-04 14:36:47 发布

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分类专栏： LeetCode

本文链接：https://blog.youkuaiyun.com/qq_34264472/article/details/77841641

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本文介绍了一种求解滑动窗口最大值问题的有效算法。通过双端队列记录当前窗口内的元素索引，实现快速查找和更新最大值。算法在每次窗口滑动时更新队列，确保队首始终为窗口内最大值的索引。

Discription:

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].

Solution:

vector<int> maxSlidingWindow(vector<int>& nums, int k) {
	deque<int> que;
	vector<int> res;
	for (int i = 0; i < nums.size(); i++){
		if (!que.empty() && que.front() == i - k)
			que.pop_front();
		while (!que.empty() && nums[i] >=nums[que.back()]) que.pop_back();
		que.push_back(i);
		if (i >= k - 1)
			res.push_back(nums[que.front()]);
	}
	return res;
}

GitHub-Leetcode: https://github.com/wenwu313/LeetCode